# Questions about water pressure regulation..



## BillyD (Mar 15, 2008)

I assume you are on city water. City could have updated equipment.
http://www.plumbingsupply.com/waterpressureregulators.html


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## 47_47 (Sep 11, 2007)

The regulator should be located in your main water line after the meter before any tees. I'd call my water authority, briefly explain the situation and ask if they did any work recently which could affect me.


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## mstplumber (May 3, 2008)

Mr. Simmons Sr.

There are several possible causes.

The first is that you do have a pressure reducing valve (PRV), or regulator, and it has just finally failed. This would explain the sudden burst of pressure when you first turn on the water, followed by a more normal pressure. Many times a failed Pressure Reducing Valve (PRV) will not just stop working altogether, but will allow the pressure to slowly creep up. Opening a faucet relieves this built up pressure.

The second possibility, which has been mentioned, is that the city has increased the main pressure. This could be due to improvements literally miles from your home and still affect you. 

A third possibility is Thermal Expansion, which is an increase in pressure due to water being heated in a closed system. Although this is a possibility, this would mean that something has been changed in your individual water distribution system, such as the city replacing the meter or installing a backflow preventer. Even if this was the case it usually takes a fair amount of time (such as over night) for the pressure to build up. The situation you describe doesn't really sound like Thermal Expansion but I wanted to mention it in just in case.

If you want to check your pressure the best way is to go to a plumbing supply and get a pressure gauge that connects to hose threads. If you can get to the washing machine connections replace one of the hoses with the gauge. This way you are sure you are checking the house pressure if you do have a PRV, since many times the outside hose faucet is connected to the unregulated side of the PRV. You should have no more tha 80 psi. Watch the gauge for a little while to see if the pressure increases after it is installed. Once you have waited a while, get someone else to open a faucet while you watch the gauge. It should only drop around 10-15 psi when the faucet is opened. If it drops a lot then you probably have a PRV and it has likely failed.

As previously posted, the PRV should be in your main line between the meter and your first branch line. Some places they are outside, underground in a valve box. Other times they are located in the basement, trace the water line from where it enters your home. If you find one you can try to adjust it. There is usually an adjustment screw sticking out of the dome that houses the adjustment spring. Generally you turn this screw out to decrease the pressure. Turn it out all the way, open a faucet to relieve the pressure, close the faucet and re check the pressure. If it is now a lot lower start turning the screw back in until you get the pressure you want.

I hope this helps.


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## wire_twister (Feb 19, 2008)

Might sound like a funny question but, is this happening with the hot water, cold water, or both? If it is just the hot water you need to check your water heater thermostat and temp and pressure relief valve. Has any work been done on the water heater lately? I had a faulty t&p valve on mine, after having the thermostat relpaced the water pressure would build and blow a glass out of your hand when you turned it on. The thermostat was not pushed tight to the tank when it was replaced causing the overheating throw in the faulty valve and there you have it, lucky i did not have an explosion.


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## mstplumber (May 3, 2008)

*You are lucky!*



wire_twister said:


> Might sound like a funny question but, is this happening with the hot water, cold water, or both? If it is just the hot water you need to check your water heater thermostat and temp and pressure relief valve. Has any work been done on the water heater lately? I had a faulty t&p valve on mine, after having the thermostat relpaced the water pressure would build and blow a glass out of your hand when you turned it on. The thermostat was not pushed tight to the tank when it was replaced causing the overheating throw in the faulty valve and there you have it, lucky i did not have an explosion.


Wow, you must be living right, wire twister. Check out this video where a couple of plumbers sraightwired a 12 gallon electric water heater and capped the T&P. Watch the tank in the last camera angle.

http://www.waterheaterblast.com


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## MrSimmonsSr (Jun 24, 2008)

*Thanks!*

Thank you all for your valuable feedback! I'll go looking around for the regulator when I get home tonight and let you all know what I found.

Thanks again!


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## uskrums (Mar 16, 2009)

*What now?*

I am having the same problem. High initial water pressure followed by normal. I went through 2 TPRVs on the water heater (both failed and were leaking water out the pipe to the outside) before I replaced the PRV. Installed the new PRV and just recently replaced another TPRV on the water heater. This is in 3 years. No banging of the pipes, just the first 3 seconds are a higher water pressure. Put a guage on the system (outdoor pipe that is after the PRV) and normal pressure is 60psi, but after a fe hours I come back and the temp needle is at 140 to 160. I have tried turning down the PRV but the overall pressure declines while the initial pressure stays high. My neighbor has an expansion tank on his water heater, but one on mine was never installed. Would this help? Does the PRV need to be replaced again?

Thanks


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## hidden 1 (Feb 22, 2009)

Hi.it sounds like a prv is at hand ,and an expansion tank if the water co put a check valve in at the meter(wouldnt hurt to ask).My pressure spiked after that was done.Prv/tank helped. I also found out a 2nd line to another faucet was not teed off main line entrance into home but tapped in way before it -it reads 80 sometimes 120.( i have to tap into other cold line for that).
Be sure to compare spikes and psi from each line/compare to water heater psi.
Oh yea- prv/tank are not hard to install


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## uskrums (Mar 16, 2009)

Yes, I guess I will call again to the water co because I haven't asked them about the check valve. I have asked about the inlet water pressure and they just say it is in the range of 80-200 so I need a PRV. Replaced it once before, hard to believe it needs to be replaced again after about 2 years if that. One guy suggested I get a more robust one next time if I am in an area with a high inlet pressure. Any suggestions? And I assume the water company will know if there is a check valve at the meter or would they have to come out and check (is it something I can look for?)

Thanks!


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## uskrums (Mar 16, 2009)

Also, when I went to the home improvement store, the directiosn for the PRV said something like this: 

*How to determine Thermal Expansion* 
When high house pressure is evident, open a cold water faucet. If your pressure gauge shows immediate drop to the regulated reduced pressure setting it indicates the regulator is operating correctly end that thermal-expansion is the cause of the expanded pressure. For additional detailed information, send for folder F-RV.

In all cases, my pressure always comes back to normal after a faucet is turned on. Since I have a PRV shouldn't I have an expansion tank? The PRV acts as a check valve doesn't it? My neighbor has one, but I never did. I keep thinking this may be the problem and not the PRV. The guy at the store said it sounded like a bad PRV as well, but I keep coming back to what the instructions say that came with the PRV...


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## uskrums (Mar 16, 2009)

Here's another article on thermal expansion. 
Thermal Expansion​When water is heated it expands. For example, the volume of water in a 50 US gallon hot water
heater will increase by almost one gallon when heated from 40ºF (4.4°C) to 140ºF (60°C). Heating
water results in a decrease in density and thereby an increase in volume (see below). Since water
is not compressible, the extra volume produced by expansion must go somewhere.​Temperature vs. Volume​Residential plumbing systems with pressure reducing valves, backflow preventers or other one-way
valves create closed systems that do not allow the water to flow back into the municipal water
supply. Therefore, system pressure increases​​​​.​
Thermal expansion of water, combined with the incoming water pressure, in a closed plumbing
system may cause unusually high pressure and pressure surges in the system. Excessively high
water pressure can result in the chronic or continuous dripping of a temperature and pressure (T&P)
relief valve, dripping faucets and leaking toilet tank ball cock fill valves.
Excess water pressure can also cause damage to the inner tank of the water heater such as
distortion of the flue and water connections. A collapsed flue can lead to the products of
combustion spilling into living spaces creating an extremely dangerous situation. Damaged water
connections may leak and a distorted inner tank may rupture and cause flooding (see below).
Thermal expansion can be managed by installing either a thermal expansion tank or a water relief
valve with a setting that is lower than the water heater Temperature & Pressure (T&P) relief valve*
setting. An expansion tank allows the increase in water volume to enter the tank until the system is
opened or the water cools down whereas a relief valve allows the water to exit the system in to a​suitable drain or discharge location.


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## JDC (Mar 11, 2008)

A pressure reducing valve with or without a check valve/backflow preventor creates a closed system. On all closed systems you need a thermal expansion tank. Your lack of one is most likely the cause of all the T&P valve failures.


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## kenmac (Feb 26, 2009)

Have any of you guys seen a prv go bad & by pass increasing water pressure in the home & when the water is turned on the pressure drops back to normal until mabe over night & the pressure builds back up again? I have replaced a few prvs that were bad & the above is what was happening.. After replacing prv no more problems


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## JDC (Mar 11, 2008)

Yes. The PRV goes bad, static pressure increases over a few hours (pressure in city mains normally goes up at night anyway due to decreased demand), a faucet is opened and the dynamic pressure drops to normal. Turn off the water and the static pressure begins climbing again because the device intended to alleviate this problem has failed.


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## rosejuli (Apr 24, 2009)

mstplumber - I guess I am lucky too , my water heater was installed with a copper wire sealing the PRV so it could not open. The water heater broke and that is how I found this out. The idiot who installed it could have killed me - right?!


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## kenmac (Feb 26, 2009)

A safety device should *never be *tampered* with..*I read the post wrong. I thought you were talking about T&P


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## RegeSullivan (Dec 8, 2006)

MrSimmonssr,

I think you should get a pressure gauge before you make any changes in you system. What you describe sounds more like air is getting into the line. Most likely for work being done up stream of you home. Gas (air) under pressure acts much differently than water under pressure because are compresses where for all practical purpose water does not. The energy in the compressed air at 60 or so psi could cause exactly what you describe. Anyway for a couple of $$ get a gauge and see what you are really dealing with .

Rege


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## rosejuli (Apr 24, 2009)

the valve that is suposed to release pressure in the hot water tank was wired with a copper (mechanically twisted)wire and the installer either neglected to remove it or just didn't know what he was doing I guess cause now I know my hot water heater could have gone off like a rocket in my house!!!!


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## Bry (Dec 1, 2012)

hey plumbers . I have a hammering pipe upstairs in the wall or floor. the water pressure kind of slows then it seems that the pressure increases and we get a hammering in just that one pipe even when doing the dishes in the main floor kitchen. any ideas?


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## Alan (Apr 12, 2006)

Bry said:


> hey plumbers . I have a hammering pipe upstairs in the wall or floor. the water pressure kind of slows then it seems that the pressure increases and we get a hammering in just that one pipe even when doing the dishes in the main floor kitchen. any ideas?


Start a new topic please as this one isn't really relevant to your situation.


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## jbenedi (May 13, 2017)

This morning my sprinkler system was turned on and immediately following, I had no water pressure. 
Last year I had my regulator replaced because my pressure was up to 140lbs.* 
After itwas replaced it was set at 50lbs.* 
The first regulator was defective (My pipes would vibrate when the water was turned on).* 
It was replaced and it's been great ever since.
Last year, I had even had out water co. out to check things out but they didn't find anything.
Today, I had no water pressure when trying to use my washing machine, kitchen faucet and bathrooms.* 
I had the plumber out who replaced it last year and he said it had suddenly spiked back to 140 lbs again and he has no idea why.* 
He adjusted it down as far as possible but wanted me to contact the Water co. because he thinks the pressure coming in from the main line is too high or there is sand or debris coming in from the main line.
Any thoughts on this issue?


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