? Home water pressure and needing Pressure Regulatory valve

Discussion in 'Water Heater Forum, Tanks' started by Tired-of-septic, Feb 4, 2013.

  1. Tired-of-septic

    Tired-of-septic New Member

    Messages:
    9
    Location:
    Tn
    I had a plumbing company come back out due to issues with my water heater, it would release small amount of water usually at night out the temperature/pressure release valve ontop of the water heater. two days prior the company also installed a EXPANSION TANK WITH WATER HEATER to solve the problem, (it didnt solve it, it still has some small amount of water coming off the TPR valve).(over 12hr period,small amount) So they came out today to recheck it, and now they say the water pressure at the back of the home's water spicket is fluxualting to 100psi. i'm assuming this is really high, and there wanting to install a pressure regulator. they looked under the home, unable to find one. It's Questionable that if i have one , they say it would be located in behind the drywall next to the front of the home's water spicket. This home was build in 1964, and was "flipped" five years ago. so i'm assuming they installed new plumbing and would they have to place a pressure regulator on the line? I just didnt know if its worth tearing up drywall looking for a pressure regulator, any idea's where or how to locate it easily or to have them install one,there quoting a price of 325.00 and one last question, why is it that if i'm having issues with high water pressure,i run one water sprinkler in the back of the home, and the one in the front dont have enough pressure to work properly?
    sorry for being wordly, thank you for your help.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    The supply can vary over time. It is often higher at night when people are no longer using water and the utility may be pumping water into the towers for the supply for the next day.

    IF you have a closed system, an expansion tank should keep the house's water pressure very close to the street pressure (it will keep it from rising more than a little bit). The T&P valve is designed to open at 150psi OR if the temp exceeds 200-degrees. I doubt your WH is exceeding 200-degrees! So, the only way to know if the T&P is defective, or is actually doing its job is to monitor the water pressure for say a 24-hour period or more. At HD, you can buy a water pressure gauge that has a tattle-tale, second hand that shows the peak pressure. It's cheap, typically around $11 or so.

    To make a closed system, there has to either be a check valve on your supply, or a PRV (pressure REDUCTION valve, not a regulation valve). When working properly, a PRV will prevent the INCOMING (not house pressure inside) from exceeding its setting. Once that water is IN the house's system, any expansion caused by heating could raise the pressure above what the PRV is set for - that is what the expansion tank is supposed to take care of.

    If you have an existing PRV, it may be worn out. It won't hurt to install a new one somewhere in the line if you already have one. Normally, if an old one is buried somewhere, it won't affect your overall volume and water pressure coming in, but it might make noises.

    It's bad practice to bury it in the wall since it may need to be adjusted or replaced eventually - they DO wear out, and it WILL need service eventually, just as will the expansion tank.

    A PRV will not raise the street pressure, but it can lower it. One is required if the incoming water pressure ever exceeds 80psi (this does not mean internal pressure that may be caused by expansion in a closed system, the expansion tank, properly setup, should prevent expansion from raising the pressure more than say a pound or two).

    You may be noticing the effects of the water being expanded now with the new WH because the new one may have a bigger burner, which raises the temp (and thus the expansion) faster. If there were any leaks in your old plumbing, say a faucet dripping, or a flakey toilet fill valve, they may have been able to bleed off that excess water (and therefore pressure) as fast as it was produced by heating. The new one, being faster to heat, they can no longer mask that problem.

    Do not confuse pressure with volume. Both a soda straw and a fire hose could have the same pressure, but the fire hose will dispense LOTS more water than the soda straw. You may have not only a pressure issue (why the T&P is opening) but also a volume one. That could be caused by a too small supply, rusting out galvanized steel supply line(s), a valve not fully open, a crimped line, and other things.

    As to costs to install, most here try to avoid that, as labor rates vary considerably all over the country, and often from one side of town to another.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    A regulator should NEVER be hidden behind drywall. It is usually located adjacent to the main water shut off valve where water enters the house. IF there is one hidden, and defective, it needs to be found because it will cause further problems to leave it.
  4. Tired-of-septic

    Tired-of-septic New Member

    Messages:
    9
    Location:
    Tn
    Thank you for your help, I went to HD and got the water pressure gauge. Since the plumbers been out there's no water from the temperature pressure valve on top of the water heater. I did recheck the water pressure in the spicket in the back of the house closest to the water heater it was 100 psi. I checked in the front closest to the main water line it was 65-70 psi. Any suggestion why the difference, and is it bad to have such high psi on the back spicket. The section of the house that has the water spicket on the back with the 100 psi is a add on addition to the original house, could there be different size of plumbing to cause the difference in psi from the front to back? Is the reason that I get small amount of water from the temperature pressure valve at night is because no one is using the water in the middle of the night and its releasing build up of pressure?
    Last edited by a moderator: Feb 4, 2013
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    It's possible your water coming in has a PRV. Some people like the high pressure for the spigot, and tap off before a PRV that feeds the rest of the house. That's the only good reason I can think of why the pressure isn't the same everywhere in your home.

    The typical pressure rise from expansion only occurs after you use hot water, (obviously) that water is replaced with colder, denser liquid, and then it is heated and expands. Once it is heated, the expansion stops. So, once the WH is off, any change in water pressure is likely from the utility. With a properly working system that includes a PRV and an expansion tank, the pressure will stay at the setting of the PRV unless the utility pressure drops below your setting. For example, your normal incoming pressure is 100#; you have your prv set to 60#. If for some reason, the utility pressure dropped to 50#, so would your house pressure - the PRV doesn't magically make pressure, it can only reduce it from the source. A WH can increase the pressure because it expands the incoming cold water when it heats it for storage, but that expansion normally is absorbed by the expansion tank, keeping the pressure almost constant. If the tank isn't large enough for the size of your WH, instead of compressing the air in the bladder, it may end up trying to expand the steel tank, it won't happen! and then, the pressure could rise. This is one reason why I say, when properly installed...both the size of the tank must be correct (bigger is okay, too small isn't) AND the air pressure in it must be proper. The proper air pressure is your 'normal' house water pressure. You can only check that when the water side of the tank is not pressurized by the water in the pipe - you must have the water turned off and a faucet open. Then, you can check the pressure just like a tire, and adjust it with a bicycle pump (a compressor might inflate it too fast, and rupture the bladder. Whenever the tank is in it's normal operating condition (i.e., the water is on), the air pressure in the tank will be the same as the water pressure which is why you can't check it when the water is on to determine the pre-charge on the tank. Just like you shouldn't check a tire on your car after you've driven for awhile...the heat will expand the air and give you a false reading...the static air pressure in an expansion tank doesn't show the actual air pressure of the pre-charge, only the water pressure after it is compressed by expansion during heating of the water at the WH.
  6. Tired-of-septic

    Tired-of-septic New Member

    Messages:
    9
    Location:
    Tn
    Since this a new hot water heater (6months old), why are I'm having problems with the temperature pressure release valve on the water heater . My old one same brand didn't do this. Checked again this morning and the TPR released small amount of water last night.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    You question has been asked and answered more than once but you don't seem to believe the answers...the valve opens because of too high pressure OR too high temp (or, it's defective). This valve is NOT designed for regular releases, and if it happens, once you fix the problem, it's usually a good idea to then replace the T&P valve with a new one. Have you left the pressure gauge on for 24-hours or more? IF so, what was the peak pressure reading? You could connect it to the drain of the WH (careful, it will be hot when you try to remove it later!), or unscrew a hose from your washing machine and install it there, or maybe a utility sink. Or, if you buy some adapters, you can install it at a faucet after taking the aerator off.

    If the valve opens and the pressure hasn't peaked at 150# or so, the T&P is defective, or the expansion tank is either not installed properly, or is defective.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,481
    Location:
    Cave Creek, Arizona
    Your pressure readings are intriguing, because if anything the one at the main should be equal to the rear, or higher. A lower reading implies a pressure valve for the house and the rear hose faucet having a direct connection to the main ahead of the regulator, but we would have to see your piping to make a definitive diagnosis. The heater would NOT "drip" water until the pressure was near 150 psi, and if it did it for anything other than "thermal expansion" it would be a "flow", not a drip, until the "problem" was relieved..
  9. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,895
    Location:
    NW Ontario, Canada
    The pressure readings suggest that there is a pressure regulator and so it is a closed system that then needs an expansion tank. T&PR valves are not designed for frequent relieving of pressure and because of a lack of expansion tank initially, it damaged the T&PRV to the point it now leaks and needs to be replaced.
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