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PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
AGE of PLUMBING MATERIALS & FIXTURES
AIR DISCHARGE at FAUCETS, FIXTURES
ANTI SCALD VALVES
ANODES & DIP TUBES on WATER HEATERS
BACKUP PREVENTION, SEPTIC
BACKUP PREVENTION, SEWER LINE
BACKWATER VALVES, SEWER LINE
BATH & KITCHEN DESIGN GUIDE
CHEMICAL CONTAMINANTS in WATER
CHEMICAL ODOR SOURCES
CHLORINE IN DRINKING WATER
DEBRIS in WATER SUPPLY, Water Heater
DEPTH of SEPTIC TANK
DRAIN & SEWER PIPING
FAUCETS & CONTROLS, KITCHEN & BATH
FAUCETS, OUTDOOR HOSE BIBBS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR DRAIN / TRAP ODORS
FLUSHOMETER VALVES for TOILETS URINALS
GAS PIPING, VALVES, CONTROLS
GALVANIC SCALE & METAL CORROSION
HARD WATER - SOFTENERS
HEAT TAPES, Heat, Insulation prevent Freeze-Up
LEAD POISONING HAZARDS GUIDE
LEAD IN DRINKING WATER, HOW to REDUCE
METHANE GAS SOURCES
MIXING / ANTI-SCALD VALVES
MUNICIPAL WATER PRESSURE IMPROVEMENTS
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
ODORS, SEPTIC or SEWER
ODORS SEWER GAS in COLD WEATHER
ODORS, SULPHUR SMELL SOURCES
ANIMAL or URINE ODOR SOURCE DETECTION
PIPING IN BUILDINGS, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING NOISE CONTROL
PLUMBING VENT DEFINITIONS & CODES
PLUMBING VENT DEFECTS & NOISES
PUMPS, WATER REPAIR
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks
REPAIR BURST LEAKY PIPES
METHANE GAS HAZARDS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SHUTOFF VALVE LOCATION, USE
SULPHUR & SEWER GAS SMELL SOURCES
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
WATER, WELLS, WATER TANKS: TESTING GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMPS & TANKS
WATER SOFTENERS & CONDITIONERS
WATER SOURCE ALTERNATIVES
WATER SUPPLY & DRAIN PIPING
WATER SHUTOFF VALVE LOCATION, USE
WATER SHUTOFF VALVE, WELL PUMP
WATER TESTS, CONTAMINANTS, TREATMENT
WELLS CISTERNS & SPRINGS
WINTERIZE A BUILDING
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.
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For steam heat piping noise, see BANGING HEATING PIPES RADIATORS. Also see NOISE CONTROL for PLUMBING and SOUND CONTROL for PLUMBING for an extensive list of causes and cures of building plumbing noises. Reproduction of this web page electronically at other websites is prohibited.
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.
We divide water hammer or banging pipe noises in buildings into two categories:
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 can damage 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
Cures for Water Hammer or Air Hammer - Hydrostatic Shock Noises in buildings
Again quoting our admired hydraulics expert Brian Boman,
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
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 buildijng is heated with steam radiators (see STEAM HEATING SYSTEMS), the noise you hear may be due to water hammer in the steam piping system. 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 (see STEAM VENTS), then making the radiator hot. Inside the hot radiator steam condenses back to water as heat is radiated (by the "radiator") into the room.
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 (see LOW WATER CUTOFF CONTROLS) , a key boiler safety device, simply shuts down the boiler.
Other causes of heating system noises are discussed at HEATING SYSTEM NOISES.
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Frequently Asked Questions (FAQs) about Water Hammer problems in building plumbing systemsSome of the FAQs discussed below are adapted from information provided by the Watts Regulator Company in a 1973 publication.
Question: does water hammer in my plumbing system cause damage?
What effects can water hammer have on my house plumbing system? Other than making noise, does it actually hurt anything?
Water hammer causes a sudden "banging" of water supply piping that creates movement and stresses in the system, not just annoying noise.
Water hammer can cause loosening of water supply piping connections, leading to plumbing leaks and related damage
Water hammer shocks to the water supply system are more serious at higher operating pressures. On hot water heaters the TP valve is usually set 20 to 30 psi above the anticipated maximum system water pressure. This is high enough that the relief valve won't leak or spill when water hammer occurs in thte system. But at higher water pressures, say 70 psi to 90 psi, the relief valve may be damaged or leak when water hammer occurs. At our article on WATER PRESSURE REDUCER / REGULATOR you 'll see that we recommend against operating a home at pressures above 70 psi because of the increased risk of plumbing system or plumbing fixture leaks.  paraphrased
Question: will the Temperature & Pressure relief valve protect the hot water tank against water hammer damage?
Will the T&P valve protect the tank against breaking from excessive water hammer? - Watts
An "excessive" water hammer is an abnormal but momentary condition that causes a very brief surge in water system pressure. The pressure-relief component of a temperature and pressure relief valve can only discharge a verly limited amount of the surged pressure during the moment of shock of the water hammer event, possibly none.
If water hammer is causing frequent opening of the temperature and pressure relief valve there may also be a risk that the frequent passage of hot water through the valve deposits scale that eventually accumulates to a level at which it prevents safe reliable operation of the valve in an emergency.
And the fact that temperatures inside the hot water storage tank are elevated above cold water temperatures makes no difference - with the exception of the warning we issue next.
Watch out: if the hot water tank is in an abnormal overheated condition, that is water in the tank has become superheated above its atmospheric boiling point water hammer could actually lead to a water heater tank explosion. According to Watts Regulator Company, "Water hammer conditions are believed to be a partial factor in starting off an explosion of overheated tanks besides "pressure heat rupture".  paraphrased
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