Water pressure or flow rate variation:

This article describes the causes of variation in building water pressure for homes connected to municipal or community water supply.

These different causes for variation in water pressure help tell us what is needed to improve or regulate the pressure.

The process of water pressure problem diagnosis and the costs of the repair are explained.

What are the Possible Causes of Variation in Building Water Pressure?

Distinguishing between static water pressure, dynamic water pressure, and water flow rate can help diagnose water problems in a building. Here we explain these concepts and we describe how to measure water pressure and flow at a property where either municipal water supply or a private well and pump water supply is in use.

The water pressure regulator setting [public water supply] may not be the same as the water pressure you'll actually get in the building.

Depending on the size of the building, its piping size and length of piping runs, and the number of fixtures and number of occupants (and similar variables) in a building, it is possible to draw water out of the building supply piping at such a high rate that the overall building water pressure drops considerably below the pressure setting at the water pressure regulator.

The water pressure settings on your [private water supply] well pump pressure control switch may not be the same as the water pressure you'll actually get in the building.

Similarly, the private well pressure control switch settings define the maximum and minimum water pressure you may see in the system, not the water pressure you'll see at any given moment when water is being run.

Even if every component of the private well, water pump, and water pressure tank and plumbing system are working normally, water pressure in such a building will fall between the time water is turned on and the time that the well pump is turned on by the pressure switch.

1. Number of plumbing fixtures being run at once: With a municipal water supply as well as private well water supply systems, the building water pressure seen at any individual plumbing fixture will vary depending on how many fixtures are being run. We tend to see this effect more on private well water systems where the total water supply system flow rate may be more limited.
2. Variation in municipal water delivery pressure: the municipal water system pressure may vary in the street as well as a function of level of water use in the whole community or when work is being done on the system.
3. Variation in small community water systems and private well pump water delivery pressure: with a small community well system as with private well and pump water supply, water pressure will also vary depending on the water pump on and off cycle and possibly on the ability of the well to deliver water.
   
   For example, if you turn on water at a sink just after the well pump has cut out the building water pressure will be at its "cut out" pressure maximum, typically 40 psi or 50 psi. But if water has been run in the building to drop water pressure in the system to just a bit above the water pressure control's "cut in" pressure, then the water pressure observed will be lower, perhaps just above 20 psi. Details are
   
   at PUMP PRESSURE CONTROL ADJUSTMENT.
4. Water pipe diameter, length, elbows and bends: Water flow rate in a building also depends on the diameter, length, and number of bends or valves in the piping system. And if water pipes become clogged with mineral deposits or debris, the water flow rate will diminish in the building, even if the static water pressure remains high.
   
   See DEFINE STATIC WATER PRESSURE
   
   and DEFINE DYNAMIC WATER PRESSURE
   
   Technical note: The D'Arcy-Weisbach equation for pressure and head loss can be used to calculate the actual water pressure loss due to friction in a building piping system.
   
   The Engineering Toolbox provides the
   
   D'Arcy-Weisbach formula: Δp = λ (l / d_h) (ρ v² / 2)  where Δp = pressure loss (Pa, N/m²), and l = length of duct or pipe (m) and d_h = hydraulic diameter (m) and finally, ρ = density (kg/m³).
   
   But keep in mind that even this apparently accurate calculation of the effect of piping on water pressure loss will not include the effects of obstructions in building water piping such as mineral deposits, debris, or blobs of solder from an improperly-soldered copper pipe connection.
5. Clogged water pipes reduce water flow rate, not water pressure.
6. Variations in building occupancy levels: Where building demand for water flow varies widely, a single pressure reducing valve may not be able to handle the maximum water demand flow rate.
   
   This condition occurs at buildings where there is a large water supply main to an apartment or office building whose water demand can vary enormously (0.5 gpm to 100 gpm) depending on the building occupants. Watts and other pressure reducing valve producers recommend a nice solution to this problem.
   
   As we explain
   
   at WATER PRESSURE REDUCER / REGULATOR, parallel pressure reducing valves are sometimes installed to correct this difficulty. One pressure regulator control is set at a higher psi flow rate than the other.
   
   For example installing a Watts Model 223 pressure reducer set at 50 psi in parallel with a second Watts 223 pressure reducer set to 60 psi will allow increased total water flow capacity during periods of peak water demand.
7. A failed hot water pressure expansion tank or significant changes in hot water temperature may also cause surges in building water pressure: some building plumbing systems include an expansion tank on the water supply system, often on the hot water piping (details about these expansion tanks are
   
   at WATER PRESSURE REDUCER / REGULATOR).
   
   If the expansion tank suffers an internal failure such as a perforated bladder, the tank will stop functioning, will not protect the system from temporary increases in hot water pressure. Also
   
   see HOT WATER PRESSURE EXPANSION RATE.
8. Water filter clogging: if your water system includes a cartridge-type water filter, typically installed to control or reduce sediment, debris, or odors, the filter may become clogged over time, resulting in a reduced water flow rate.
   
   Some folks confuse water flow rate (how fast water comes out of the tap) with water pressure (static pressure when water is not being run). And lots of people call our water flow rate "water pressure" which it is, in a practical sense - the pressure with which water comes out of the tap.
9. Variation in performance of the pressure regulator itself: a water pressure regulator may be misbehaving.
   
   One water pressure regulator failiure mode causes gradual increases in building water pressure above the set point on the regulator. This may be due to an internal failure or leak in the water pressure regulator, dirt on the regulator valve seat, or a leak in an internal regulator valveo pressure-sensing diaphraghm.
   
   See WATER PRESSURE REGULATOR TESTING for a discussion of regulator tests and possible repair procedures.
10. Variations in private water supply source, well capacity, and well pump behavior will also cause variations in water supply pressure on private well water systems.
    
    See WELL WATER PRESSURE DIAGNOSIS
    
    and WATER PRESSURE CONTROL SWITCH ADJUSTMENTS.
    
    Problems with the private well itself are discussed beginning
    
    at WELLS CISTERNS & SPRINGS.

Readers whose building is served by a private pump and well system should also

see WATER PUMP PRESSURE CONTROL.

How do we Diagnose Poor Municipal Water Pressure & Flow in a Building - 5 Key Checks

Key things to check when water pressure and flow are inadequate in a building served by municipal water supply are

1. The condition of individual plumbing fixtures, faucets, valves, and controls. A clogged sink or shower strainer will cause bad water pressure at individual fixtures while others may flow freely. A plumbing shutoff valve that is partly closed or clogged with debris will cause bad water flow at that fixture.
2. The incoming municipal supply pressure. The municipal water supply source may be delivering water at low pressure.
3. The condition of water piping between the building and the street water main. An older water supply pipe connecting the building to the water main in the street may be small in diameter, clogged with minerals, rust, or debris, or it could be leaking underground.
4. The condition of building water supply piping. Clogged pipes due to minerals or rust, small diameter piping, long piping
   
   For details about the above items,
   
   see MUNICIPAL WATER PRESSURE DIAGNOSIS
5. The setting of the water pressure regulator at the building water meter or water shutoff valve. This topic is discussed just below.

Bad water pressure regulator or bad pressure regulator adjustment: (poor municipal water pressure) if the building is connected to a municipal water supply there may be a water pressure regulator installed, usually close to the water meter or where the water supply pipe enters the building.

Photos of water pressure regulators and diagnosis and adjustment advice are

at WATER PRESSURE REDUCER / REGULATOR.

If the water pressure control was set too low to start with or if there is a problem with the water pressure regulator, you may see an improvement in water pressure by diagnosing and adjusting or repairing this control.

If the loss of water pressure was sudden, it's not likely to be a problem the pressure regulator except in the less common cases of a blockage or failure in the regulator itself. In this photo our flashlight lights up a (rather amateurish looking) water pressure regulator installed on a municipal water supply.

You can see that a previous connection to the water meter was cut, left shut off (see that shutoff valve at the left hand vertical pipe - what happens if someone opens that valve?), and new fittings were installed to conduct incoming water to the building water supply piping.

The use of smaller diameter flexible copper tubing might restrict the incoming water flow, but the presence of a pressure regulator at all suggests that the incoming pressure may have been excessive. (Too high water pressure leads to fixture leaks.)

How to Adjust the Water Pressure Regulator on Municipal Water Supply

Details about how to adjust the building water pressure regulator or pressure reducing valve are found

at WATER PRESSURE REGULATOR ADJUSTMENT.

We have already mentioned checking and adjusting the pressure control for the water pump on a private well system - just above. But what if the home does not have it's own well - what if the building is connected to a municipal water supply?

Watch out: don't set the water pressure reducing valve higher than necessary. Doing so wastes water and as we discuss

at WATER PRESSURE TOO HIGH: DANGERS, setting water pressure too high can cause both plumbing problems and actual serious safety hazards at buildings.

A Guide to Building Water Pressure by Adjusting or Repairing

the Water Pump Pressure Control Switch on a Private Pump and Well Water Supply

For details about diagnosing poor well water pressure and flow, start

at WELL WATER PRESSURE DIAGNOSIS or go directly to the individual items listed just below.

• How to Adjust Water Pump Pressure: The detailed, step by step procedure for inspecting and adjusting the water pressure control switch is discussed in detail
  
  at ADJUST PUMP PRESSURE CONTROL.
• Diagnosing Water Pump Short Cycling on and off: If your water pump is clicking on and off too often or quite rapidly
  
  see SHORT CYCLING.
• Diagnosing Water Pressure Drops without explanation when the pump stops,
  
  see WATER PRESSURE FALLS SLOWLY, ERRATIC PUMP: bad pressure control switch, building water running or leak, bad pressure gauge, bad check valve, bad foot valve.
• Diagnosing & Repairing Lost Air in the Water Tank: The problem of lost air in the water pressure tank along with how to correct that condition are discussed beginning
  
  at SIGNS OF AIR LOSS.
• Diagnosing & Repairing a Water Pressure Control or Water Pump Control Switch: We discuss diagnosing and repairing a water pressure control switch that sticks "on" or "off" or simply won't operate,
  
  at WATER PUMP PRESSURE SWITCH REPAIRS

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-04-24 by (mod) - Codes & Standards for Required Maximum & Minimum Water Pressure at Buildings - UPC Chapter 6

Bottom line: excerpting/adapting from UPC 608.1 Inadequate Water Pressure

• the minimum water pressure in the building (after a pressure boosting system if one is necessary) is 15 psi and
• the maximum building water pressure (in the building, after any pressure regulators) is 80 psi.

Watch out: higher water pressures not only invite leaks at fixtures, high pressure can burst a pipe or water pressure tank, flooding the building or injuring a bystander. That's why you'll also find in the model codes a requirement for a pressure relief valve on any pressurised water tank.

@Yosafad V,

I'll be glad to help Yousafad, but to be clear

Nowhere in the article above do we assert a requirement for a specific water pressure as a regulator standard;

We cite information from manufacturer's installation instructions for pressure control devices and we describe reasons that water pressure varies - which is the purpose of this particular article.

In the U.S. the model code agencies (not ASTM) set and discuss safe water pressure levels for buildings.

Instead, you'll find minimum and maximum water pressure along with related safety guidelines in the model plumbing codes as well as in the actual codes adopted by various statse (U.S.) or provinces (Canada).

For example under IAPMO Uniform Plumbing Code we protect from unsafe (too high) water pressure (no more tha 80 psi) as well as assuring a minimum functioning water pressure (15 psi).

There are also strainer and repair access requirements for pressure reducing or pressure regulating valves.

Notice that the focus is on regulating pressure DOWN to a safe level. That's not a requirement to deliver water TO the building at a particular pressure nor flow rate.

You'll also find this in the Uniform Plumbing Code that in turn is adopted in various municipal codes.

The example water flow table I include below is excerpted from Utah's adoption of the

Uniform Plumbing Code, UPC, Chapter 6-water supply and distribution (2015) [Utah]

available from that state's government,

UPC CHAPTER 6 WATER SUPPLY & DISTRIBUTION (2015) as adopted by Utah [pdf]

and also at BUILDING CODE DOWNLOADS - free PDF downloads.

Here are examples of additional pressure-regulating code citations from the same source. "Pressure" appears nearly 130 times in Chapter 6 alone. So what follows is not exhaustive.

UPC 604.7 Inadequate Water Pressure [as adopted by Utah]

Wherever water pressure from the street main or other source of supply is insufficient to provide flow pressures at fixture outlets as required under Table 604.3, a water pressure booster system conforming to Section 606.5 shall be installed on the building water supply system.

UPC 604.8 Water Pressure-Reducing Valve or Regulator

Where water pressure within a building exceeds 80 psi (552 kPa) static, an approved water pressure-reducing valve conforming to ASSE 1003 or CSA B356 with strainer shall be installed to reduce the pressure in the building water distribution piping to not greater than 80 psi (552 kPa) static.

Exception: Service lines to sill cocks and outside hydrants, and main supply risers where pressure from the mains is reduced to 80 psi (552 kPa) or less at individual fixtures.

...

UPC 605.3 Water Service Pipe

Water service pipe shall conform to NSF 61 and shall conform to one of the standards listed in Table 605.3. Water service pipe or tubing, installed underground and outside of the structure, shall have a working pressure rating of not less than 160 psi (1100 kPa) at 73.4°F (23°C).

Where the water pressure exceeds 160 psi (1100 kPa), piping material shall have a working pressure rating not less than the highest available pressure. Water service piping materials not third-party certified for water distribution shall terminate at or before the full open valve located at the entrance to the structure. Ductile iron water service piping shall be cement mortar lined in accordance with AWWA C104.

UPC 605.4 Water Distribution Pipe

Water distribution pipe shall conform to NSF 61 and shall conform to one of the standards listed in Table 605.4. Hot water distribution pipe and tubing shall have a pressure rating of not less than 100 psi (690 kPa) at 180°F (82°C).

605.6 Flexible Water Connectors

Flexible water connectors exposed to continuous pressure shall conform to ASME A112.18.6/CSA B125.6. Access shall be provided to all flexible water connectors.

605.7 Valves

Valves shall be compatible with the type of piping material installed in the system. Valves shall conform to one of the standards listed in Table 605.7 or shall be approved. Valves intended to supply drinking water shall meet the requirements of NSF 61.

606.5 Water Pressure Booster Systems

Water pressure booster systems shall be provided as required by Section 606.5.1 through 606.5.11.

606.5.1 Water Pressure Booster Systems Required

Where the water pressure in the public water main or individual water supply system is insufficient to supply the minimum pressures and quantities specified in this code, the supply shall be supplemented by an elevated water tank, a hydropneumatic pressure booster system or a water pressure booster pump installed in accordance with Section 606.5.5.

Watch out for this important safety feature:

UPC 606.5.10 Pressure Relief for Tanks

Every pressure tank in a hydropneumatic pressure booster system shall be protected with a pressure relief valve. The pressure relief valve shall be set at a maximum pressure equal to the rating of the tank.

The relief valve shall be installed on the supply pipe to the tank or on the tank. The relief valve shall discharge by gravity to a safe place of disposal.

UPC 608.1 Inadequate Water Pressure.

Where the water pressure in the main or other source of supply will not provide a residual water pressure of not less than 15 pounds force per square inch (psi) (103 kPa), after allowing for friction and other pressure losses, a tank and a pump or other means that will provide said 15 psi (103 kPa) pressure shall be installed.

Where fixtures, fixture fittings, or both are installed that require residual pressure exceeding 15 psi (103 kPa), that minimum residual pressure shall be provided.

What about ASTM standards about water pressure?

As you refer to ASTM standards I'll guess that you're a reader in the U.S.

ASTM produces standards for testing - it is NOT a building code nor is it a model code itself, though model codes may sometimes refer to various standards-writing agencies and their specific standards (ASTM, NSF, etc.)

There is no ASTM standard for the "required" or even "recommended" water pressure delivered in a building (though there are pressure limit safety standards, for example on your water pressure tank and on various equipment and on water piping and controls)

Example ASTM Standards Discussing Pressure Ratings

• ASTM F645 - 18b Standard Guide for Selection, Design, and Installation of Thermoplastic Water- Pressure Piping Systems
• ASTM F2261 - 06(2018) Standard Test Method for Pressure Rating Poly(Vinyl Chloride) (PVC) Plastic Pipe Fittings, Schedule 40 and 80 Socket-Type.
• ASTM F1370 - 92(2019)e1 Standard Specification for Pressure-Reducing Valves for Water Systems, Shipboard
• ASTM F2389 - 19 Standard Specification for Pressure-rated Polypropylene (PP) Piping Systems
• and ASTM has a whole collection of Water Testing Standards - for contaminants in water

In addition to the links given in the article above, there are more citations at the "click to show or hide" references at the end of any of our articles.

On this particular page where you are reading, that's at

Technical Reviewers & References

And at BUILDING CODE DOWNLOADS

you will find copies of model building codes and plumbing codes as free PDF downloads.

On 2021-04-24 by Yosafad V - regulations about pressure standards

I love this Information, Thank u for all of you

i'm just have one question, can you guys explain and provide me some information regarding the source of the information that has been given, especially regarding regulations about pressure standards for sanitary or also static pressure standards, is this based on ASTM? if i'm right, what is the ASTM code?
Thank you

On 2018-11-05 - by (mod) -

Usually what you describe is due to clogged piping.

Sure you can rule out the water softener as a contributor by putting it in bypass except, darn-it, for the odd case to which you hint: a clog in the bypass valve itself.

On 2018-11-05 by RICH

The water pressure is great & steady when using one faucet! When two are used it drops en half,on both hot & cold. Have a 20 yr.

Old salt type water softener! Could this be my problem? Or pressure regulator, or? If I bypass the softener that would rule it out? Could the regulator be partially plugged up?

On 2017-09-14 by James

Adjusting the pressure regulator on my residence changes the flow into the system but the highest pressure achieved is consistently 110 psi.

The psi before the regulator (water source) is 110psi. Adjusting the bolt (?) only changes the lower psi value when the system is open. Lengthened (outward) causes a larger variation (e.g. 0-110psi) with the low being achieved when the system is open and the maximum when closed.

Shortening (inward) results in a smaller variation (e.g. 75-110psi), again with the low being achieved when the system is open and the maximum when closed. I have not tried to adjust to a position all the way in. The in and out notations are correct for the flow into the system.

Assuming that the regulator is faulty but wanting to check and see if there is another explanation.

On 2017-03-04 - by (mod) -

Richard, I can't make an objective assessment of noise by an e-text but if the pressure is extreme - say over 70 or 80 psi there is risk of leakage or even a burst pipe - worth correcting. And of course we're probably wasting water unnecessarily too. The problem could be a failed, missing, or improperly-set pressure regulator. That's worth a mention.

On 2017-03-04 by richard

In the hotel building l reside in there are 12 flats (1 room) with toilet etc.. When the water comes out the pressure is enormous, it does in fact make a real whooshing noise which ruins the locale mileau so much, that one has a whim to mention to the NOT professional maintenance person " maybe the water pressure is way too high?" What do you think? comf38@gmail.com

On 2017-02-25 - by (mod) -

Jerry you will need to use a pipe pressure drop calculator. There is no single right answer from just the paramaters you give. For example you need to give additional data specifying water flow rate and pipe material or assumptions on the smoothness of the pipe interior.

On 2017-02-23 by Jerry Gill

How much water pressure is lost for every twenty feet of straight pipe, 90 deg. elbow, and 45 deg. elbow in a 1 inch copper line?

On 2016-01-18 by Dawn

Water pressure is fine when first turned on. Then slows to a trickle or off for a few seconds until pump kicks in then all is fine. Also wash machine and toilets take forever to fill up. When you flush toilet, takes a few seconds for pump to kick in, then fills up.

Question: Water pressure varies while taking a shower; sometimes the warm shower gets too cold

I get a noticeable water flow variation, especially during a shower. When the well pump kicks in it over powers the hot water significantly making a warm shower cold. Any ideas what I should do?

Reply: Regulating water temperature at the shower during normal pump operating cycles

If your hot water runs too cool when the water pump turns I suspect that your hot water piping or hot water source is clogged - perhaps if you are using a tankless coil that is mineral clogged this would be more likely. You could install an automatic mixing valve right at the shower - that valve is designed to keep water temperature constant; first try partly closing the individual cold water shutoff valve for your bathroom - by this I mean a valve in the cold water line that is "ahead" of or before the shower itself. By restricting the cold water flow rate in the piping you may improve the pressure balance.

But overall I suspect the problem is more likely to be clogging in the hot water piping or hot water supply system. That's because the PRESSURE produced by the pump is the same at both hot and cold water piping. It's the FLOW through piping systems that is more likely to vary. A similar effect is found when you're in the shower and someone flushes a toilet or turns on cold water at a nearby sink - and you are suddenly scalded.

If you think your hot water piping is clogged

see CLOGGED SUPPLY PIPES, HOT WATER.

It is normal for building water pressure to vary between 20-40 psi or 30-50 psi depending on how your pump pressure control switch is set. Even after you've de-clogged your hot water supply you can make a still better improvement in regulating water temperature at the shower by installing an anti-scald device or valve, either at the hot water source or right in the bathroom at the fixture.

See ANTI-SCALD VALVES for details.

Question: our water pressure comes on fast but quickly drops off to nothing. Is this a clogged pipe problem?

OMG my farm house was built before christ and my pressure gauge on my well has 60 psi works fine except I don't have any pressure in the house, I can turn on a faucet and it fast then drizzles down to nothing and if the kitchen sink is running there is next to none in bathroom, if filling washing machnine there is no water upstairs untill the washer fills up. takes at least 5-7 minutes for toilet to fill and 20 for the tub. How can I get the rust out of my pipes w/o tearing the house apart. I believe that they are clogged with rust since it is hard well water. - Lisa

Reply:

Lisa if you have no actual water pressure but the gauge is reading showing pressure is present, and provided no one closed a water valve between tank and house, I suspect that the gauge pressure reading is wrong and the gauge is stuck. Try tapping on the pressure gauge to see if it moves.

The same crud that clogs the valve can clog the pressure sensing switch and interfere with proper well pump operation. If it's a rust and sediment problem your plumber might install a filter ahead of the rest of the water equipment.

Take a look at CLOGGED SUPPLY PIPING, but because the water pressure falls off quickly you'll also want to be sure that the water pressure tank is not waterlogged, causing the well pump to have to turn on and off too frequently.

See WATER PUMP SHORT CYCLING to diagnose well pump short cycling and water pressure that rapidly rises and falls.

If on the other hand water pressure falls off and takes a long time to recover, I suspect that the well itself is running out of water.

For that problem see WELL FLOW RATE and also how to measure the flow rate or recovery rate of a well.

Follow-Up:

Thank you Mr. Friedman I will certainly try that with a light touch upon looking into the well I saw a capusule looking clear plastic part rustly what is that called and maybe that needs to be replaced I posted this alittle while ago and it didn't show up I turned all water off waited opened all faucets turn back on and no water b/c all faucets were open left only kitchen and water hardly any rust or air not like it use to when we hard power failure as no lights no water. Thank you for helping me, Lisa

Question: high water pressure, varying pressure, & burst components led to a leak

5/19/15 LB said:

All while back I had a problem with my water line bursting at my water meter. It happened on a day when the municipality had turned off the main water to all the rural area. When the water was turned back on, my line burst. I checked my water pressure at the meter and it is 102 PSI. Is that within a reasonable range? I also have a regulator in my home that was installed prior to me purchasing the property. From what I can gather, the previous owners had problems with seals and valves blowing, hence the regulator.

(May 20, 2014) Dale said:

I am on a municipal system with a pressure reducing valve in line. Most of the time the pressure gauge on the house plumbing lines would read 50-60 psi, however I had a problem with the water pressure creeping up to over 100 psi. Simply turning on the water for a few seconds would drop the pressure back down. Looking at the gauge later it could be normal or over 100 psi. I changed the pressure regulator with a new one and it's doing the same thing again. Any suggestions?

Reply:

Indeed 102 psi is quite high and would be expected to give recurrent leaks at fixtures inside a building IF the building's water pressure regulator was not working or was not properly adjusted.

Watts corporation as well as other manufacturers produce a wide range of pressure reducing & regulating valves.
Usually a "direct acting" pressure regulator is what's installed in homes.

For high pressure commercial operations one might need to install a pilot-operated pressure regulator but in a private home that has very high incoming or widely varying water pressure it's more likely that a 2-stage pressure reduction that I will cite below is what's needed. Watts.com describes these products from which I paraphrase or adapt:

Direct acting valves, the more popular type of a water pressure reducing valves, consist of globe-type bodies with a spring-loaded, heat-resistant diaphragm connected to the outlet of the valve that acts upon a spring. This spring holds a pre-set tension on the valve seat installed with a pressure equalizing mechanism for precise water pressure control. - retrieved 5/19/15, reference source http://www.watts.com/pages/learnAbout/reducingValves.asp?catId=64

You certainly need a pressure reducing valve that can handle the pressure range your municipality delivers, which might mean installing two valves in series - a two-stage, "serial reduction" pressure reduction system. You don't
usually need two stages unless the incoming water pressure varies and is sometimes at 200 psi or higher.

In sum, I suspect the problem is that the original pressure reducing valve you had installed was either improperly selected, adjusted, or perhaps it just failed.

Question: poor shower pressure

(Oct 22, 2014) doug said:

i have a private well tyhat was installed in 1998, it has started recently having good pressure then dropping off almost to nothing then jumping back up. this just started

(Nov 10, 2014) Steve said:

My water pressure is low in the shower until I turn on another device. If I turn on one of the sinks in my bathroom the pressure in the shower goes up and back to how it used to be.
Any ideas? I have a fancy valve from Kohler but that was ruled out. I have 2 other heads in there and it acts the same even without the main. 2 plumbers can't figure it out...Help!

Reply:

Russ I see a question from Steve - is Russ = Steve?

Low shower pressure: if that's the only fixture suffering - start by removing the shower head and checking the flow. If flow is good clean or replace the shower head. If flow is poor there is a blockage in the line to the shower or one of its valves.

When turning on another fixture improves water pressure I can but infer that the added flow turned on the pump.

Question:

12/1/2014 John Schult said:

Replaced pressure switch (40-60) Added 38psi air engaged new switch ran for 15 seconds then stopped. Waited 1 1/2 minutes re-engaged power did same thing will not run complete cycle. ?

Reply:

Sounds as if the tank is water-logged or water is not able to enter the tank. Or the tank was simply nearly full. Try running some water in the building.

Question: water pressure in the system varies too much

2016/09/17

I have a water system based on a tank plus demand pump. The problem at the moment is that the pressure in the system varies too much between full pressure and the cut in of the demand pump. i.e. while taking a shower the water temperature drops markedly. What is the problem? - Anonymous by private email.

Reply:

Then watch your pressure control and pressure gauge as water is running to see if the pump is turning on when the pressure falls to the pressure switch CUT-IN pressure setting. If not the switch is clogged or damaged and needs replacement. Do let me know what questions remain after that and I'll be glad to research and respond in detail. - Editor.

...

Continue reading  at WATER PRESSURE REGULATOR ADJUSTMENT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see WATER PRESSURE VARIATION FAQs - questions & answers posted originally on this page

These

Recommended Articles

• WATER PUMP PRESSURE CONTROL - on a private well or on a water pressure booster pump sysetm
• WATER PRESSURE CONTROL SWITCH ADJUSTMENTS - private pump & well pressure controls
• WATER PRESSURE REGULATOR ADJUSTMENT - municipal water supply pressure

Suggested citation for this web page

WATER PRESSURE VARIATION CAUSES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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