Banging pipes & water hammer noise diagnosis, cure:

Water hammer noises in plumbing is also called hydrostatic shock. Our page top photo shows a water hammer noise suppression device produced by Oatey and available at building suppliers.

This particular water hammer noise suppressor is interesting because it's designed to be added to a hose bib or washing machine hose connection by a homeowner, avoiding having to cut and solder pipes.

The articles at this website will answer most questions about plumbing noise associated with water hammer or water surge, including the diagnosis and cure of water hammer noises as well as many other building plumbing system inspection or defect topics.

Water Hammer Noises in buildings: Diagnosis & Cure

Water Hammer & Banging Pipe Noise

What is water hammer noise - also called "air hammer" noise in pipes & how do we stop this source of banging clanging pipes?

We divide water hammer or banging pipe noises in buildings into two categories: water hammer in the plumbing system and banging pipes in hot water or steam heating system.

In this article starting just below we describe water hammer and hydrostatic shock in house plumbing systems, typically water supply piping but also in irrigation systems, pools, spas.

[Click to enlarge any image]

Image of correcting water hammer noise (above) provided courtesy of Carson Dunlop Associates, a Toronto home inspection and education company.

Below we discuss the following: Definition of water hammer or hydrostatic shock noise in plumbing pipes. How to diagnose & cure water hammer noises & banging pipes. Curing water hammer by adding an air chamber or surge buffer. Where to buy water hammer noise suppressors, where & how to install water hammer or water shock noise suppression devices.

Curing water hammer by draining pipes to restore air charge in risers. Diagnose & cure other water supply & Drain Piping Noises. Sources of water hammer noise suppression devices. Plumbing supply and drain piping system inspection, testing, & repairs.

Note: other causes of banging booming noises in buildings, not traced to the building plumbing or water supply system itself, are addressed at

BANGING BOOMING NOISE DIAGNOSIS & CURE - home - other sources of bangs booms in buildings - and include for example, banging radiators and banging noises at steam heating systems.

How to Diagnose & Fix Water Hammer Noises in House Plumbing Systems

Definition & Actual Cause of "Water Hammer" Noise

Water hammer (or hydrostatic shock) is a noisy pipe problem that occurs when valves are shut off quickly. You may hear banging water pipes, or clanging, rattling, or rumbling noises in the water piping when a plumbing fixture, sink, or clothes washer turns off.

Here is a more scholarly definition of water hammer that is rather clear:

Water hammer is a hydraulic phenomenon that is caused by a sudden change in the velocity of the water. This velocity change results in a large pressure fluctuation that is often accompanied by a loud and explosive noise. This release of energy is caused by a sudden change in momentum followed by an exchange between kinetic and pressure energy.

The pressure change associated with water hammer occurs as a [shock] wave, which is very rapidly transmitted through the entire hydraulic system. Severe or repeated water hammer events can lead to pipe failure.

The sudden change in velocity caused by the rapid closing of a valve can produce very high pressures in the piping system.

These pressures can be several times the normal operating pressure and result in burst pipes and severe damage to the irrigation system [Dr. Boman's interest, but also impacting any plumbing system - Ed.].

The high pressures resulting from the water hammer cannot be effectively relieved by a pressure relief valve because of the high velocity of the pressure wave (pressure waves can travel at more than 1000 ft per second in PVC pipe). - Boman (2014)

High Velocity Water Flow Rates Can Cause Water Hammer

Think of water screaming along at 100 mph: it's doing pretty nicely until it hits a curve (maybe a pipe elbow) or a wall (a valve that has suddenly shut). Then SLAM!

Watch out: if the velocity of water in your piping system is too fast, when faucets or other controls STOP that water flow you may hear a horrible hammering or banging in the piping system. Water hammer is more than a horrible noise, it can damage equipment, cause potentially dangerous leaks at temperature/pressure relief valves, and may even cause a divorce.

Keep in mind that where pipes are poorly supported, or where equpment such as pumps, valves, controls anywhere in the water supply system are causing variations in the water flow rate, you may hear a horrible banging water pipe noise even when the water valve itself is not being suddenly closed.

In a hotel in Mexico City we heard an incredible vibrating banging noise in water pipes in the wall near our bathroom whenever the sink faucets were opened. Opening to run water either faster or slower can often stop that banging/vibration problem.

Leaks from water hammer traced to high water velocity are also discussed

at CLOGGED SUPPLY PIPES, REPAIR .

Watch out: When Increasing Water Flow Rate or Velocity or GPM, such as when adding a more powerful water pump or when adjusting a water pressure regulator to give faster water flow at fixtures, watch out for both water hammer & water scrubbing damage.

High Velocity Water Flow Rates Can Cause Scrubbing Damage & Water Piping Leaks

A second problem with very high water velocity rates through building piping is scrubbing or wearing away of the pipe interior: a problem that occurs at very high water speeds (measured in feet per second) in piping systems.

Generally the maximum safe water velocity or speed in residential water piping systems is 7 feet per second, and for 2-inch or larger pipes you should not exceed 5 feet per second.

Some piping types such as PEX (CTS SDR-9) at smaller diameters such should have flow rates limited still further.

3/8" PEX should be limited to 3 gpm at 10 ft³/s. [CTS = copper tube size and SDR = standard dimension ration of pipe wall thickness to pipe diameter].

Scrubbing is more of a worry in metal piping than in the smoother (less friction) plastic piping systems. Scrubbing and corrosion are common sources of pinhole leaks in water supply piping.

Convert Flow Rates in GPM to Flow Rate in Feet per Second

Note: to convert between cubic feet per second of water flow into gallons per minute we need to know just two magic numbers:

1 minute = 60 seconds

1 cubic foot = 7.5 U.S. Gallons

A flow rate of one cubic foot per second, then will give us 7.5 gallons per second or in a minute, 60 x 7.5 = 450 gallons per minute. That's a lot of water.

Notes to the table above

That's not so fast, right. But water hammer can still occur. At these flow rates, water pipe scouring problems are unlikely. Higher water flow rates and velocities are found in some residential sprinkler systems and possibly in other special equipment where scouring could be a concern.

Note that for a fixed pipe diameter, changes in water pressure will produce a corresponding change in flow rates.

To convert any of our GPM numbers to litres per minute (LPM) multiply GPM x 3.78.

Resource: Stryker, Jess, "Increasing Minimum Available GPM", - retrieved 5/13/15, original source: http://www.irrigationtutorials.com/faq/increase-irrigation-gpm.htm. Mr Stryker is a landscape architect practicing in California.

Stryker provides a table for irrigation system designers who need to know maximum recommended water flow rates in GPM for various types of pipe and pipe diameters. That data will not pertain to most residential interior plumbing systems.

Water Hammer Can Also Occur even at Low Water Velocity Rates

Drip Irrigation System Timer Causes Water Hammer

Really? Water hammer noises can occur in a building piping system even when the water supply is turned off: the main water shut-off is closed. What on earth could explain that?

A combination of residual water pressure in the building piping system and anything that turns water flow on and off such as a timer-operated watering irrigation system can be enough to cause water hammer.

While water hammer is associated with both high water velocity and often a rapidly-closing water valve, the operation of a water valve can cause a hammering noise even when water velocity is low and water pressure is modest.

Reader Anonymous (by private email) described this case to us:

I had a water hammer going in my house even after shutting off the mains. Yes!!. It was a water hammer and it really drove me crazy. I ultimately diagnosed it to a faulty sprinkler timer on the faucet outside my house which was controlling drip irrigation.

It had failed and it was trying to switch on the value and turn it off intermittently and the quantity of water in the lines was sufficient to result in shock even though the mains were shut. And since there were drippers at the other end, it took a while for the water to drain out sufficiently.

I thought I would let you know so that you can update your site with the hope that it will help others. Your site was one of the first ones that I visited to diagnose the issue.

Bottom Line : anything that turns water on & off can cause water hammer noise

Anything mechanical or electrical which can turn water supply on & off on can cause a water hammer, especially when it is failing. It is hard to diagnose this as the appliance can be outside your house or even batter operated. - 2017/10/25 anonymous by private email

Reply:

With the water main off I'm surprised that anything would produce water hammer - at least as I know it, since the sound requires a certain velocity of water running in pipes followed by a sudden closing of a valve.

Are you saying that the water supply system remained pressurized enough to cause water hammer until the sprinkler system drained down?

Reader follow-up:

Yes. I too was surprised. I too thought that enough water velocity is required. And it seems there is sufficient pressure in the lines. One thing that I must mention that there are only a few 1/2 GPH drippers on the sprinkler/irrigation line and there is a pressure controller too on the line.

I wouldn't have believed this myself but I can "reproduce" the issue.

The moment I turn on the faucet connected to the battery operated irrigation controller, the hammer comes back and keeps going for a while even after the mains are turned off.

If I leave the mains on, the hammer never goes away. It is as-if there is a ghost in the pipes.

How Water Hammer Can Damage Water Pipe or Pipe Connections and Result in Leakage

In more layman-like terms, water hammer works like this: water passing through a pipe has momentum or velocity. When the valve is shut quickly, the momentum of the water carries it into the valve with considerable force.

Since water is essentially incompressible, a large pressure is built up against the valve, and there is low pressure upstream in the pipe. The high-pressure water wants to flow to the low-pressure area.

This happens so quickly that a small vacuum is created against the valve as the water moves away from it. This can result in cavitation as the water is pulled back against the valve a second time. This continues back and forth in slowly diminishing shock waves.

Pressures up to 600 psi (some sources say 1000 psi) can result from water traveling up to 3,000 miles per hour, for very short periods.

Water hammer can result in loud noises in supply plumbing pipes. Water hammer only occurs as valves are closed. If a valve is closed slowly, and the noise does not occur, one can be sure that water hammer is the problem.

Water hammer is common with quick-closing electrically operated valves on appliances such as washing machines and dishwashers. Air chambers can be installed to control water hammer, as Carson Dunlop's illustration (above) demonstrates.

Causes of Water Hammer / Hydrostatic Shock Include

• Ball check valves valves used on water supply piping where the weight of the ball in the check valve is not properly-matched to the pump capacity. If water-hammer noise stops when the pump turns off, the check valve ball may be too light.
  
  See CHECK VALVES, WATER SUPPLY, DRAINS, PUMPS
• Check valve noises, particularly at sump pumps, effluent pumps, and sewage ejector pumps occur when flow reverses in the discharge pump at the end of a pump-on cycle.
  
  See SEWAGE PUMPS for details.
• Excessive building water pressure
  
  See MUNICIPAL WATER PRESSURE DIAGNOSIS
  
  or WATER PRESSURE REDUCER / REGULATOR
• Poorly supported water supply piping
• Certain fixture valves and controls may be prone to causing water hammer as they shut off high velocity flow very quickly
• Water piping that is too small for the flow rate of water through the building piping.
  
  This is more likely to be noticed if the building water piping makes long straight runs, especially vertical runs of 12 feet or more.
• Missing water hammer noise suppression device or air riser to absorb the shock of change in water velocity when water is suddenly shut off

Diagnostic Tips for Determining that Banging or Rattling Pipe Noise is Water Hammer

If you hear a rattling, banging, or clanging that seems to come from building pipes AND if the noise stops when no water is being run in the building most likely you're hearing water hammer.

Change the water flow rate

(or pressure): Try this: when you hear the water hammer noise, turn water on to increase the flow rate at one or more fixtures, OR turn the water flow rate off slightly to slow the water flow. Often changing the water velocity in the piping system will cause the water hammer to stop - a diagnostic clue.

If you hear banging pipes when no water is running (check to make certain that all water is off, including filling toilets, outdoor sprinklers etc.) then the banging noise may be a heating pipe problem that we discuss

at BANGING HEATING PIPES RADIATORS

Change the water pressure:

if water pressure is too high that can be a source of noisy water pipes and also water hammer. Drop the water pressure a bit. Does the noise change?

Correlate banging pipes to specific appliance or plumbing fixture use.

For example does flushing a toilet, closing a sink valve, or using the washing machine cause a banging noise?

Also see WASHING MACHINE NOISE CAUSE & CURE

Correlate banging noises to use of the building's steam heating system.

If you are hearing baning pipes or banging sounds at the building's heating boiler,

see STEAM BOILER FLOODING / SURGING REPAIR

Cures for Water Hammer or Air Hammer - Hydrostatic Shock Noises in buildings

Again quoting our admired hydraulics expert Brian Boman,

The best prevention of water hammer is the installation of valves that cannot be rapidly closed and the selection of air vents with the appropriate orifice that do not release air too rapidly. Pipelines are usually designed so that velocities remain below 5 fps in order to avoid high surge pressures from occurring. - Op. Cit.

• Try draining the building water supply piping:
  
  if your building supply piping includes one or more air risers - vertical water pipes that end in a cap or stub - you may be able to stop water hammer noise by draining the building piping to re-admit air into the riser pipe.
  
  This should fix the problem for several years though eventually air in the riser may become absorbed into the water and need to be recharged.
  
  If your air risers don't keep working there may be a plumbing air leak in the building piping system.
• Try adding a water hammer arrestor or noise suppression device sold at building or plumbing suppliers.
  
  Water hammer arrestors are designed not to lose their air charge. Install the water hammer arrester at or close to the plumbing fixture or faucet that seems most to cause the water hammer noise. We list suppliers of water hammer suppression devices below.
• Adjust the building water pressure: if the building water pressure is too high, water hammer noise may be more likely.
  
  If water pressure is 80 psi or higher you almost certainly need to install a pressure regulator or adjust the existing one to a lower building pressure setting..
  
  See WATER PRESSURE REDUCER / REGULATOR.
• Check the support for building water supply piping:
  
  water pipe noises may also be due to excessive movement (which also risks water pipe leaks), especially if your water supply piping is copper or another metal. (Plastic water supply piping is pretty quiet).
  
  All piping and tubing should be adequately supported with hangers. Copper piping should not be supported with steel hangers because of the corrosion that will take place.
  
  Copper pipes should not contact heating ducts for similar reasons. Plastic piping and tubing should be well supported and be kept away from heat ducts.
  
  If you need them, sound isolating plumbing pipe mounting fixtures can reduce noise transmission.
  
  See details at PLUMBING NOISE TRANSMISSION CONTROL
• Check for air in the piping system
  
  A well and pump that are not working properly or other sources of air in water pipes can cause banging, bubbling, burbling noises in the plumbing system
• Check for other banging noise sources:
  
  The banging that you hear may not be due to general water hammer problems but may be caused by a malfunctioning appliance or plumbing fixture.
  
  For example see our discussion of causes of banging sounds at
  
  WASHING MACHINE NOISE CAUSE & CURE

adapted from Carson Dunlop Associates The Home Reference Book & used with permission.

Also see SOUND CONTROL for PLUMBING for an extensive list of causes and cures of building plumbing noises.

Also see NOISES COMING FROM WATER HEATER for the diagnosis and cure of clanking or thumping noises that may be coming from your water heater or heating boiler.

- Adapted with permission from The Home Reference Book

Eight Steps to Stop Water Hammer Noise & Water-Hammer-Caused Plumbing Leaks

or Plumbing System Damage in Buildings

The sink faucets shown above were installed by the author; in some countries these simple valves are referred to as "jumper" valves.

The following list of water hammer elimination advice is an expansion of material from multiple sources including those cited throughout this article and atReferences or Citations .

1. Install a pressure regulator
   
   to keep building water supply pressure below accepted limits (500kPa in Australia)
2. Install a water hammer eliminator
   
   between the building water supply piping source and the highest or most-distant plumbing fixture or point of use.
3. Install water hammer suppression devices at each automatically-operated appliance
   
   water flow control solenoid or valve such as at washing machines and dishwashers.
4. Use ball valves in place gate valves
   
   or "jumper valves" where possible.
   
   Ball valves close more smoothly and less abruptly than some other designs. Also install ball valves to control water flow at shutoffs or at points of use where the fixture valve is normally open (such as at toilets)
5. Use sound isolating piping supports,
   
   mounts or clips when routing water piping.
   
   When penetrating a stud, if using a sealant for sound isolation, be sure it is distributed uniformly around the pipe. Also see Kwolkoski (2006)
6. Install soft-closing water valves at fixtures
   
   or other points of use.
   
   See PLUMBING CONTROLS & VALVES
7. Spring-loaded valve washers:
   
   Where typical point-of-use fixture water control valves (jumper valves in Au) are in use, install spring-loaded washers in the valve body.
8. Pipe support:
   
   Clip all pipes as per AS NZS 3500.

Also see SOUND CONTROL for PLUMBING

Reader Reports Saga of Searching for an End to Water Hammer at the Water Heater (Cylinder, Geyser)

9/12/2014 Bruce Reid said:

I have a brand new water heater which i rent from my utility company. Ever since they installed it, i've had water hammer noises on all fixtures in my house be they hot or cold. At first I thought the noise was just a loose pipe, so I called the utility to come and re strap the pipes tightly to the joists like they were before. The new heater is in a slightly different position than the previous one so they had to pull the pipes down a few inches.

They also used Shark Bite connectors this time around. That's the only difference I can see. So now I have this hammer noise on any faucet or toilet in the house, and even the outside garden hose.

The noise is loudest RIGHT NEXT to the water heater. If i turn off the water supply to the water heater all the noises go away. so that means it's the the heater's fault, right? My questions are these:

1) Why would a new water heater cause WH noises even on cold lines?

2) Should the utility have to pay for this?

3) The instructions for the arresters are to put them near the fixture that is causing the noise.

Well ALL fixtures can trigger it, but i'm pretty sure I'd blame the heater. Would it be wise to install an arrestor right at the cold water intake of the water heater?

Reply:

Bruce,

Your diagnosis is important and helpful but maybe not the last word. The water hammer may be due to the velocity of water entering or leaving the heater - not the fault of the heater itself.

Try slightly closing the cold inlet to the heater to see if that fixes the trouble. If it doesn't you'll want to install one or more water hammer prevention devices ahead of or after that appliance.

• SHARKBITE INSTALLATION GUIDE [PDF] (2018) Reliance Worldwide Corporation 2300 Defoor Hills Rd NW, Atlanta, GA 30318 Phone: 1-877-700-4242 Fax: 1-877-700-4280 rwc.com Reliance Worldwide Corporation (Canada) Inc. 74 Alex Avenue Vaughan, Ontario, L4L 5X1 Phone: 1-888-820-0120 Sales Inquiries: canadasales@rwc.com Orders: canadaorders@rwc.com retrieved 2019/08/13 original source: https://www.sharkbite.com/sites/g/files/rgohfh321/files/2018-05/SharkBite_Installation_Instructions_2018_WEB.pdf
• SHARKBITE ENGINEERING SPECIFICATIONS [PDF] Op. Cit. incudes detailed, photo-illustrated SharkBite fittign installation instructions.

Reader follow-up:

9/13/14 Bruce Reid said:

Hi Dan, thanks for the tip.

I turned it halfway off this morning and am still hearing the banging, and i'm not sure if it's my imagination or not, but there seems to be a related "echo bang" now. Instead of one loud bang, i hear 2 small ones.

I'm going to experiment with this a bit more at different levels of closure of the cold water inlet.

Still. Old water heater- no noise. New water heater - lots of noise. One can only assume that it's the water heater's fault right? As i was saying, the only difference in my house is one new water heater, two pipes (in and out) that were slightly stretched to reach the heater and the use of shark bite connectors to the WH instead of soldering the pipes

Reply:

On track to debug, one can but ask, so what changed: just the heater, or perhaps also nearby piping; possibly the new heater replaced one whose inlet was partly clogged, slowing water flow. Or a valve was changed, or pipe routing.

Ultimately understanding water hammer (velocity and sudden stoppage) leads to either modifying flow rate or installing anti-hammer devices.

Reader follow-up:

thanks again for your continuing advice. This is really useful.

My most recent tests to help debug. I used my garden hose from outside and brought it downstairs next to my WH. I brought a 5 gallon bucket down there to fill with the hose. I submerged the hose to keep the noise down.

Water Hammer Test conditions

1. Turn water inlet to the WH completely open. (this is the normal configuration). Fill the water bucket in steady 2-3 second bursts from the hose. The result is the expected Bang followed by 1-2 smaller echoing bangs about a second later.
2. Turn water inlet to the WH completely CLOSED. Fill the water bucket in steady 2-3 second bursts from the hose. The result is SILENCE. Not a sound
3. Turn water inlet to the WH to half open. Fill the water bucket in steady 2-3 second bursts from the hose. The result is the expected Bang followed by 1-2 smaller echoing bangs about a second later.
4. Turn water inlet to the WH to 1/10th of a turn open (practically closed). Fill the water bucket in steady 2-3 second bursts from the hose. The result is the expected Bang followed by 1-2 smaller echoing bangs about a second later.

My intent here was to find that sweet spot in the water inlet valve that would reduce the sound to zero. Apparently that doesn't exist. Any opening means noise.

So there you have it. In a cold water only test, we get bangs from the area around the WH on any situation where the water inlet is open. Even just a crack.

On hot water tests, using another fixture, for example, the kitchen sink, with hot water tap turned on the bang is a bit bigger.

So if hammer arresters are the solution, where would you suggest putting them. on the cold water supply line to the WH? Note that's a bigger diameter pipe than the rest as you'd expect.

(I've run out of available text space here so I'll put more info in a later post.) thanks again!

Reply: where to install the water shock / water hammer arrestor

Nice going Bruce.

I confess that I've tried fixing water hammer by adjusting building water pressure or by controlling flow rate into an appliance like a water heater with only mixed success.

Have you tried buying a water hammer arrestor device and installing it on the water supply line near the heater? I'll summarize again the standard things to try when stopping water shock or water hammer noise in a building.

Heating Pipe Noises: Banging Pipes on Steam or Hot Water Heating Systems

Please see  our complete articles on heating system noise diagnosis and cure

at HEATING SYSTEM NOISE DIAGNOSIS

and STEAM BOILER FLOODING / SURGING REPAIR - that can cause banging steam pipes or banging at the steam boiler


and BANGING HEATING PIPES RADIATORS. Excerpts are below.

If it sounds as if someone is down in your BASEMENT or cellar banging on the heating pipes with a hammer, and particularly if your building is heated with steam radiators, the noise you hear may be due to water hammer in the steam piping system.

See STEAM HEATING SYSTEMS

In both one-pipe and two-pipe steam heat systems steam rises into the building's heating radiators, forcing air out of the radiator's steam vent , then making the radiator hot. Inside the hot radiator steam condenses back to water as heat is radiated (by the "radiator") into the room.

See STEAM VENTS

This steam condensate must drain back into the steam boiler where it is subsequently re-heated to steam to continue the heating cycle. But if the condensate is having trouble returning to the steam boiler your heating pipes may become waterlogged.

This happens because when the steam boiler water level drops and is not replenished by returning condensate, the automatic water feeder will just send more water into the boiler.

Condensate accumulating in the steam piping (when it should be returning to the boiler) not only water-logs the system, it also means that cooler condensate (water) comes into contact with hotter rising steam in the piping. This contact can cause rapid expansion/contraction in the heating pipes and produces the loud "pipe banging" noise we are discussing.

Your heating service technician should be someone familiar with steam heating systems and the proper layout and function of condensate return lines in your home. The tech will look for a problem that is blocking condensate return to the heating boiler, such as a clogged strainer in the system piping, a steam trap clogged with rust, minerals, or sediment, or a similar problem.

A separate problem: failure of individual steam radiators to get hot, could also be due to blocked condensate return.

If a radiator's steam vent is not working, or if a one-pipe steam system's radiator has settled so that it is no longer properly tipped to send condensate back into the steam pipe (and back to the boiler), that radiator will stop working. But individual radiator troubles do not usually explain banging heating pipes.

Watch out:  If your heating boiler does not have an automatic water feeder and you've been putting makeup water into the boiler manually, a blocked condensate line and low water in the boiler will eventually lead to total loss of heat when the low water cutoff switch , a key boiler safety device, simply shuts down the boiler.

See LOW WATER CUTOFF CONTROLS

Other causes of heating system noises are discussed

at HEATING SYSTEM NOISE DIAGNOSIS.

How to Choose & Install a Water Hammer Arrestor

Typically the installation instructions provided with water hammer arrestors discuss two considerations:

1. Choose the size of water hammer arrestor 
   
   depending on the number of fixtures that are likely to be running (and shutting off) at once in the building.
   
   Tables provided by the manufacturer will consider the number of plumbing fixtures and will recommend a water hammer arrestor size. Generally it won't hurt to install a larger capacity water hammer arresting device than you thought you needed.
2. Install the water shock arrestor or water hammer arresting device near (but not at) the end of a water supply branch between the last two plumbing fixtures 
   
   on that branch - for plumbing branch lines that are 20 feet or less in total length.
   
   Watch out: do not install the water hammer arrestor at the very end or uppermost end of supply piping in a building. A water shock arrestor installed in this location is unlikely to be effective.
   
   For longer plumbing supply pipe runs (longer than 20 ft)
   
    you may require at least one additional water hammer arrestor. In this case place the second water hammer arrestor at the mid point of the total length of the plumbing pipe run.
3. Install a water hammer arrestor on the supply side of particular shock-causing clothes washers or dishwashers
   
    or other appliances that are causing the water shock noise.
   
   For example you may need to install a water hammer arrestor on the supply side of a dishwasher or clothes washer. This improvement is likely to be much less costly than replacing the solenoid valve in those appliances.
   
   Tip: special water hammer arrestor devices are available that include hose connectors to permit them to be installed right at the hot and cold water hook-ups of most washing machines.
   
   Other water hammer arrestors are available using compression or press fit connectors for installers who are not handy at soldering copper pipe. Shown above, the Sioux Chief water hammer arrestor with hose thread fittings suitable for installation at a clothes washing machine.
4. Install a water hammer arrestor on both hot and cold water piping systems. 
   
   If you observe particular water hammer noise when running hot water don't forget to install a water hammer arrestor on the hot water piping system.
5. If installing a water hammer arrestor is not enough 
   
   to stop water hammer, ask an experienced plumber to inspect the plumbing system: there may be improper piping, routing, securing, or other errors that must be corrected.

Summary of steps to stop water shock or water hammer in a building

1. Install a water hammer arrestor on the piping system to absorb the shock of sudden stoppage of water flow
2. Water pressure reduction: Try reducing the building water pressure right at the pressure regulator
3. Water flow rate reduction: Try reducing the water velocity in the piping by using flow-restrictor outlets at faucets, shower heads, tubs.
   
   You can approximate this by partly closing the supply valve to a fixture. If you see that one plumbing fixture is particularly guilty of causing that banging slamming water hammer noise start there. You might try installing a flow restrictor ahead of the offending appliance or fixture.
4. Use slow-closing water supply valves: slow-closing valves are available for toilets and possibly clothes washers
5. Change water supply piping diameter (smaller) or re-route piping to use shorter pipe runs before there is a turn or bend in the piping (this may be an expensive option so it's my last choice)

Water Hammer Arrestor Size & Location Specifications

Where to install the water hammer arrestor: this information is now found

at WATER HAMMER ARRESTOR LOCATION & SIZE

Water Hammer Arrestor Plumbing Codes, Installation Guides & Instruction Manuals

This information is now found

at WATER HAMMER DEVICE CODES & MANUALS

Where to Buy Water Hammer Arrestors - water hammer suppression products

This data is now found

at WATER HAMMER DEVICE SOURCES

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-01-22 - by (mod) -

If you've pinpointed the noise to a specific wall it may be time to take a look into the wall: by cuts or a boresope; or you might want to bring an experienced building inspector or sound engineer onsite. We need to relate the apparent noise sources you suspect that seem in your log to be disparate.

We assembled your Noise Log data vertically simply so that it could be read by most viewers.

[Click to enlarge any image]

On 2021-01-22 by Denise

I did upload a noise tracking spreadsheet for yesterday....the noise happens so often I'm not sure doing it for a week would lead to any different data points.

Have you able to review it?

The main source of noise is in the wall between the 2 bathrooms (approx 15' in length) so I'm not too sure I'd be able to pinpoint it much further with a mechanical stethoscope unless I cut into the drywall.

On 2021-01-22 - by (mod) -

For a confounded noise track down such as the situation you describe, even though it's difficult, the most-profitable course of action is a combination of

- locating the noise source by amplitude (instruments can help)

- locating noise sources by noting what equipment is running or not running

| - relating noise to exterior conditions: temperature, sunlight, weather, air movement, occupancy, etc.

For that the noise log I cited earlier and that you've attempted (example above) can help

On 2021-01-22 by Denise - It's definitely not water hammer

It's definitely not water hammer as the first plumber ruled that out. The house was built 2009. I did look at the links you shared but nothing jumped out. If it's due ducts expansion, how could it be that the banging occurs when I haven't used the furnace for 8 hours?

Hi,
Attached is a summary. You will need to put together the pages horizontally, not vertically.
Denise

On 2021-01-22 - by (mod) -

Denise, Steve and other readers: Please find your question and my detailed reply now at the Reader Q&A section near the bottom of the article above on this page. You may need to clear or refresh your browser cache to see the updated page. We welcome your further photos, comments, questions.

On 2021-01-22 by (mod) - trouble finding source of banging pipes & alternatives to water hammer noise

Sorry, I'm guessing that you try to attach a document. Comment box only allows people to attach photos. Perhaps you can paste in a summary as a comment.

Also consider that the noise you hear may not be water hammer, but other sources of banging noises in buildings such as expanding metal duct work or HVAC noises or other thermal expansion and contraction of materials.

See these two diagnostic articles

• BANGING HEATING PIPES RADIATORS
• BANGING BOOMING NOISE DIAGNOSIS & CURE
• WATER HAMMER DIAGNOSIS
• WATER HAMMER CURES
  

On 2021-01-22 by Denise

I have poured through the resources here and have found nothing that comes close to what I'm experiencing.

I'm ready to call someone in to cut into the wall in the upper level as the sound is so unpredictable and at times can be very loud. Attached is a summary of just today and late last night....interested if you can see anything that I'm missing.

Thank you. I will look at those links later today and can perhaps upload audio. The trouble is, the sound isn't constant or always repetitive, so it's hard to know when I'll hear it again after the initial bang sound.

It can also occur when the furnace hasn't cycled for hours so it's hard to pinpoint if that is the problem or not. I'll give you an update....

On 2021-01-19 - by (mod) -

Denise

Indeed we need more sound recording and tracking work at your house; sounds caused by an event in one location such as a heating system can be picked up and transmitted by nearby materials, so ducts can conduct piping noises and vice versa.

NOISE SOURCE LOCATION - LOG FILES

and other suggestions are

at NOISE / SOUND DIAGNOSIS & CURE

On 2021-01-19 by Denise

The past 4 months I've been getting random banging sounds from under the sink in the ensuite. It can happen day/night, at times where no water has been used in the house for hours. The sound comes from somewhere along the pipe in the wall. The house was built in 2009.

Plumbers have come out, it's not water hammer although he drain all water from all taps in the entire house (heard the sound 4 hours later).

I've turned off the main water line at night and have still heard it. There is no leak, water stains, etc. The last plumber said it may have to do with heating ducts causing expansion and contraction?

(Not sure what the connection is with that, there is a heating vent in each bathroom) The sound is definitely coming from under the sink and it carries over to the pipe under the sink on the other side of the wall in the other bathroom.

I cannot find any pattern as to what triggers i (i.e. it's not after a shower or when the toilet has been flushed, etc.). Any help would be greatly appreciated as it's extremely annoying. I even hear it when I'm on the main floor as the sound comes down through the ceiling. Sometimes I don't hear it all day other times I hear it 10 times in one hour.

On 2021-01-15 by Steve

Ok thank you for your reply, much appreciated.

On 2021-01-14 - by (mod) -

Steve

I doubt that anyone can give a reliable exact explanation of the noise that you were hearing now from simply a brief text note. But it's possible that you were simply hearing normal plumbing noises that would be better isolated if there were insulation in the common wall between your two living spaces.

That may be something you can add for example by pumping or blowing in foam or a similar sound deadening material. It won't be perfect because the wall framing will still conduct some sound but it should reduce the issue.

On 2021-01-14 by Steve

I live in a townhouse with common walls, after my neighbour renovated his bathroom I can now hear when he uses the shower, which is annoying and due to his shift work is in the very early hours of the morning.

It's a loud, constant white noise type of sound rather than a hammer.

Your advice as to the cause would be greatly appreciated.

On 2020-12-24 - by (mod) -

Roland

Indeed that sound could be coming from your pump. I've encountered exactly that problem in a water system that we recently installed. It depends on the type of pump and where it is installed. Maybe you could tell me more about that.

On 2020-12-24 by Roland

Recently added a circulating line and pump to my water heater. As a precaution, I also added an expansion air tank. I am on city water, so I have great dependable water pressure. I do have an irrigation system, but that is closed off because it is winter.

Since the install of my pump, I am experiencing a tapping when a faucet is open an water flowing. I have icolated the noise to be a backflow valve, which was previously in place, but now is making a noise as if it were opening znd shutting constantly while water is flowing....approximately every "second". Could the circulation pump cause this? Could the expansion tank cause this? These are my only two main variables.

Thanks,

On 2020-12-23 - by (mod) -

Tony

Most likely one of the causes listed in the article above.

Try closing your main water valve a bit.

On 2020-12-23 by Tony

What is causing my water pipes to randomly have a low knocking noise and I just put in a new water heater about a week ago but this was going on before I put the new water heater in?

On 2020-12-17 - by (mod) -

Fred:

Thank you very much for taking the time to write this very helpful water hammer noise update.

You can teach an old dog new tricks.

I will add to our list of steps in tracking down noises in plumbing systems, meters, etc. to remember to check not just your own but other nearby water meters, pipes, etc. that may be those of a neighbour.

On 2020-12-17 by Fred O

RE: "IF water is flowing in the home but the water heater isn't registering that water use then the meter is probably damaged and that might indeed be the noise source."

I FINALLY have the answer (probably) and you were essentially right --
When the thumping noise was occurring, I checked my next door neighbor's meter, which is adjacent to mine and next to the street. I could feel the vibration there and the meter indicator was spinning rapidly and jerkily. So the problem is a meter -- my neighbor's.

I have notified the city water dept. (I rarely see the neighbor).

On 2020-11-30 - by (mod) - water meter not "water heater"

Right, and apologies Fred; we have so many readers, comments, questions that when I'm getting behind I may try dictating a reply and sometimes miss the computer's typos- embarrassing both myself and the software and hardware involved.

Don't forget to check for water that's running in secret, such as a running toilet.

On 2020-11-30 by Fred O

RE: "IF water is flowing in the home but the water heater isn't registering that water use then the meter is probably damaged and that might indeed be the noise source."

I think you meant "water meter" rather than "water heater." When water is flowing, the meter does register the flow. But since we can hear the noise only when in the garage and we normally do not run water when we are out there, the meter does not show flow when we hear the noise.

The noise is intermittent, only a few times/day. I still suspect either the meter or some unknown vibration in the water main under the street. But then, neighbors do not report hearing a similar noise.

I sent a message to the city building inspectors similar to the previous I posted here. No answer yet. I've not called my plumber since the hot water tank was replaced.

Thanks,
Fred

On 2020-11-27 - by (mod) - IF water is flowing in the home but the water meter isn't registering

Fred

IF water is flowing in the home but the water meter isn't registering that water use then the meter is probably damaged and that might indeed be the noise source.

On 2020-11-27 by Fred O

RE: "It might be interesting to use a mechanic's stethoscope on the water pipe at several locations when you are hearing the mystery noise".

Thanks again for your advice. I can feel the pipe shaking slightly where the pipe is exposed. Also see below.

Today, a new development. Rather than "thump, thump, thump" at a moderate volume, we heard "tap, tap, tap" at faster cadence and lower volume. We could also feel the tapping on the pipe but it was not as prominent as earlier.

I went out to the water meter, which is in a box just below ground next to the street and I could feel the tapping on the meter. Again, no water flowing and the spinner on the meter did not move. A bit later, the thumping returned, louder than the tapping but I think at lower volume than the thumping before.

I now suspect the meter. A week ago, I called the Prescott building inspection dept. and left a message They have not called back. I plan to leave an email msg.

On 2020-11-24 - by (mod) -

It might be interesting to use a mechanic's stethoscope on the water pipe at several locations when you are hearing the mystery noise

On 2020-11-24 by Anonymous

RE: "If there were really no water movement through pipes then what might cause pipe "noise" in the first place?"

A couple times I've looked at the water meter when the pipe was thumping but did not see any movement. Once, I noted the position of the spinner and saw it in the same spot 30 minutes later.

"Possibly some other, even outside, mechanical noise source that's being picked up and transmitted by the piping or a local pressure booster pump or there is a leak somewhere that's not been found."

I intend to try feeling the meter for vibration next time I hear the noise. But it occurs only occasionally. Only pump is the hot water recirculator and that's on a count-down timer that I installed myself. As for leaks, the water bill has not been elevated.

Tis a puzzlement. Thanks for your thoughts. I've asked my city building dept. but they have not answered my query.

On 2020-11-22 - by (mod) -

Fred

Thanks for an interesting question. I'm stumped. If there were really no water movement through pipes then what might cause pipe "noise" in the first place?

Possibly some other, even outside, mechanical noise source that's being picked up and transmitted by the piping

or

a local pressure booster pump

or there is a leak somewhere that's not been found.

On 2020-11-20 by Fred O

This is a reworded repeat of a query entered yesterday that has not appeared.

I have a somewhat different water pipe noise problem.

A couple weeks ago, I noticed noise -- thump, thump, thump, -- about 2-3 times per second and continuing for about a minute coming from the water line in my garage. The line, (PEX pipe) installed 2 years ago to replace the original line that was leaking, runs from a meter by the street, underground and then up through a hole in the garage floor to the ceiling and finally around two walls to the shutoff and pressure regulator next to the hot water tank.

The noise is not very loud. I can usually hear it only when I'm in the garage. But I can feel the pipe shaking when thumping. I'll guess it occurs a few times each day.

My plumber initially said it was caused by a failing regulator but then he found the thermal expansion tank was full of water. He attached a pressure gage to a spigot and told me to not run water until he returned in an hour with a new tank. The pressure stayed constant (~60 psi) until he returned so he replaced the tank and not the regulator.

Next day I heard the thumping again. The plumber convinced me to also replace my 16 year old Rheem water heater although in my experience, Rheem tanks last over 20 years.

But the following day and subsequently, I've heard the thumping again. Twice when this was occurring, I checked the water meter to verify no water was running. Once I went in the house and opened a faucet but the thumping did not stop right away.

The house is in Prescott, AZ and was built in 2004. The supply pressure is rather high -- 110 psi and about half of the water lines in my development have failed but I believe the failure is due to improper filling of the trenches with chunks of basalt rock rather than the proper sand bedding and shade fill.

The replacement line was properly installed and inspected by the city. Another nearby development is at the same altitude, thus likely similar pressure but homeowners there do not report water line failures. Several neighbors I've asked do not report not hearing similar noises.

What to do next?

On 2020-10-19 - by (mod) -

Les

Knowing nothing about your home and its environment we're left with my best shot at an organized list of things to check for water hammer as given on the page above.

Please take a look there as a good place to start.

If anything you find at InspectApedia seems incomplete, confusing, or wrong please ask - or complain as it'll help us both.

On 2020-10-19 by Les

Have done the following to try and fix water hammering problem: changed valve kits, flappers etc., new water inlet hoses, new pressure valve, inspected roof vents, drained system, installed hammer arrestors. Still have the problem, ANY IDEAS? Help!

On 2018-07-02 - by (mod) - Your website is a miracle worker!

Marge

Thank you as well for taking time to let us know that our information on water hammer was helpful to you. I recall the drip irrigation comment and at the time figured, well what the heck, maybe this odd-sounding problem isn't so unusual after all. So we moved the remarks into the article above. I'm especially glad that in the enormous sea of web pages you were able to find the information.

We welcome as well questions, criticism, and content suggestions: working together makes us smarter.

Thanks again.

Daniel

On 2018-07-02 by Marge Davis - the problem was a faulty outside water timer trying to start a drip irrigation system.

Your website is a miracle worker! An hour ago we started hearing a periodic "thump" from the laundry room--followed it to the washer's cold water line, where we could feel and see the pulse as well as hear it. After trying several completely useless remedies (tested the water pressure, turned on faucets simultaneously, etc.),

I found this website, scrolled through the discussion and came upon a comment from a reader with the same mysterious noise who determined that the problem was a faulty outside water timer trying to start a drip irrigation system.

Sure enough, that was our problem as well. The batteries were depleted enough that the system couldn't kick on. Thank you so incredibly much for this resource and freely shared expertise!

...

Continue reading  at WATER HAMMER ARRESTOR LOCATION & SIZE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see WATER HAMMER NOISE FAQs questions & answers posted originally at this article.

Or see these

Recommended Articles

• AIR DISCHARGE at FAUCETS, FIXTURES - air in the plumbing system may cause banging noises in pipes
• BANGING BOOMING NOISE DIAGNOSIS & CURE - home - other sources of bangs booms in buildings
• BANGING HEATING PIPES RADIATORS
• CHECK VALVES, WATER SUPPLY, DRAINS, PUMPS - can reduce water hammer
• FOOT VALVES - home
• PLUMBING NOISE CHECKLIST
• WATER HAMMER NOISE DIAGNOSE & CURE - home
  • BANGING HEATING PIPES RADIATORS
  • BANGING HEATING SYSTEM NOISES
  • BANGING HEATING ZONE VALVES
  • DEFINITION of WATER HAMMER
  • HIGH VELOCITY WATER HAMMER
  • HIGH VELOCITY WATER SCRUBBING DAMAGE
  • FLOW RATES in GPM CONVERT to FEET PER SECOND
  • LOW VELOCITY WATER HAMMER
  • HYDROSTATIC SHOCK PIPING LEAKS
  • STEAM BOILER FLOODING / SURGING REPAIR
  • WATER HAMMER DIAGNOSIS
  • WATER HAMMER CURES
  • WATER HAMMER at GEYSER / WATER HEATER CURED
  • WATER HAMMER vs HEATING PIPE NOISES
  • WATER HAMMER ARRESTOR TYPES
  • WATER HAMMER ARRESTOR LOCATION & SIZE
  • WATER HAMMER DEVICE CODES & MANUALS
  • WATER HAMMER DEVICE SOURCES
  • WATER HEATER NOISE DIAGNOSIS, CURE

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WATER HAMMER NOISE DIAGNOSE & CURE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING NOISE DIAGNOSIS

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