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MrSimmonsSr 06-24-2008 09:34 AM

Questions about water pressure regulation..
Hello all! Thanks for taking the time to read my thread. I'm somewhat handy and have repaired my own appliances and such, but I know absolutely nothing about plumbing, so I'm coming here to ask you guys about this issue.

I have a home that I moved into in 1997. The water pressure within the home has always been very reasonable and proper. In the last 2-3 months, however, I have started noticing that when the water isn't running a large amount of pressure builds up in the water system. When I get up in the morning now and turn on the shower there is about a 2-3 second burst of high pressure that causes the joints on my shower head to leak and spray out water. After this initial burst, the pressure seems normal. The same thing happens whatever outlet I open. When turning on the kitchen sink after a short time of non use, the water pressure is initially so strong that it blows the small directional nozzle off of my sink head.

So something has happened in the last 2-3 months that has caused the water pressure in my system to not be regulated properly. I'm interested in some suggestions about what you guys think might be going on. In my initial web searches I have found a bit of information about regulators and how they work. I'm wary of having to spend an arm and a leg for a plumber to come do something I could do myself, but I know that some jobs require someone who knows what they are doing. I would not feel comfortable having to cut pipe and re-solder a regulator replacement. That said, however, I wouldn't mind getting a pressure gauge, making some measurements, and making adjustments to a regulator, if my home has one.

FYI: I'm not on a sewer system and have a septic tank. I didn't think that would have much impact on the discussion, but thought I'd mention it just in case.

So my question is, where should I look for a regulator, if there is one? I don't see it in my basement (unfinished) where I would have expected it to be. Is there somewhere else I should be looking?

What else should I look for as a possible culprit as to why this just started recently. Our neighborhood is almost 25 years old now and my home was the last ones built, so I don't think any major changes have occurred in the system in a while. I could be wrong about that, however.

I'm open to any and all suggestions. Thanks for taking the time to reply!


BillyD 06-24-2008 11:22 AM

I assume you are on city water. City could have updated equipment.

47_47 06-24-2008 11:48 AM

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.

mstplumber 06-24-2008 04:56 PM

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.

wire_twister 06-24-2008 04:57 PM

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.

mstplumber 06-24-2008 05:04 PM

You are lucky!

Originally Posted by wire_twister (Post 133391)
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.

MrSimmonsSr 06-25-2008 09:25 AM

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!

uskrums 03-15-2009 08:23 PM

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?


hidden 1 03-16-2009 12:17 PM 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 :)

uskrums 03-16-2009 07:03 PM

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?)


uskrums 03-16-2009 07:21 PM

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...

uskrums 03-16-2009 07:24 PM

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 40F (4.4C) to 140F (60C). 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.

JDC 03-16-2009 08:58 PM

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.

kenmac 03-16-2009 09:14 PM

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

JDC 03-16-2009 09:18 PM

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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