Forum Thread

Plumbing : PRV & Expansion tank related

GlobWarmNoGood 349 365 May 21, 2016 at 08:45 PM
Home water pressure problem:
Had plumber replace outside waterline to 3/4 copper recently & also new PRV was installed. After that work I am having pressure issues.
Outside pressure is typically 180-200 psi.
PRV is set at 50 psi (default)
For the 75 Gallon hot water heater, there is a 2 gallon expansion tank. Open line pressure (set pressure) is 50psi.

Inside home pressure gauge readings:
when faucets running - ~46 psi
after faucets closed - 50 psi
after 1-0-15 mins - 55 psi
after couple of hours - 70-80psi - during this time having issues like thud sounds during toilet flush, high force water from faucet etc.

what could be the issue? I suspected expansion tank but after turning off inlet supply & let faucets run out, the psi shows 50psi & no water leaks from the nozzle.

Note: Last year had similar issue, replaced PRV and the leaking expansion tank and issue was resolved.

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#2
Quote from GlobWarmNoGood View Post :
Home water pressure problem:
Had plumber replace outside waterline to 3/4 copper recently & also new PRV was installed. After that work I am having pressure issues.
Outside pressure is typically 180-200 psi.
PRV is set at 50 psi (default)
For the 75 Gallon hot water heater, there is a 2 gallon expansion tank. Open line pressure (set pressure) is 50psi.

Inside home pressure gauge readings:
when faucets running - ~46 psi
after faucets closed - 50 psi
after 1-0-15 mins - 55 psi
after couple of hours - 70-80psi - during this time having issues like thud sounds during toilet flush, high force water from faucet etc.

what could be the issue? I suspected expansion tank but after turning off inlet supply & let faucets run out, the psi shows 50psi & no water leaks from the nozzle.

Note: Last year had similar issue, replaced PRV and the leaking expansion tank and issue was resolved.
If the readings are without the water heater running, then I would go with a leaking reducing valve.
Most times if the expansion tank isn't working, you'll get water dripping out of the relief valve on the water heater also.

Did you test the exp tank pressure with a tire gauge and now water pressure against it?
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#3
Quote from stufine View Post :
Most times if the expansion tank isn't working, you'll get water dripping out of the relief valve on the water heater also.
pressure relive valve leaks at 150psi I heard. mine hasn't reached that high yet.
Quote from stufine View Post :
Did you test the exp tank pressure with a tire gauge and now water pressure against it?
yes I measure at a neutral condition meaning. water coming from the city was blocked. let faucets run to relieve the pressure inside. and then measure with pressure gauge and it measured 49.5 which what I was expecting.
Thanks!.
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#4
180-200psi water pressure coming into the house is pretty dam high.

If nobody will be home, you could turn off the water heater and let the pressure rise. That would eliminate the water heater running as the source of pressure increase.

Could be PRV not able to hold back the HIGH inlet pressure. Watts recommends 2 valves if pressure 200 or if it swings a lot
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#5
Quote from stufine View Post :
180-200psi water pressure coming into the house is pretty dam high.

If nobody will be home, you could turn off the water heater and let the pressure rise. That would eliminate the water heater running as the source of pressure increase.

Could be PRV not able to hold back the HIGH inlet pressure. Watts recommends 2 valves if pressure 200 or if it swings a lot
Thanks.

~200 is sad fact here. Folks around here had to replace waterline/PRVS prematurely.

turning off water heater and checking is an option, will think about it.

LF25AUB-Z3 is the model I use and it says rated upto 300psi.

plumber replaced a new one with another PRV yesterday and rules out any issue with PRV. when he left all was well. then pressure started to creep up.

questions:
How much extra psi would heater put despite having an expansion talk typically?
assume PRV & expansion tank is set at 50psi. how much upswing in psi can be expected normally? on the lower side I see 5psi.
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#6
Cold Water Temp = 45 degrees Fahrenheit
Hot Water Temp = 135 degrees Fahrenheit
Hot Water Tank Volume = 80 gallons
Tank Pre Pressure = 70 PSI
UCPW System Water Pressure = 70 PSI
Maximum Allowable Pressure in Plumbing = 100 PSI

Press “Calculate” and the results display:
Minimum Thermal Expansion Tank Size = 4.46 Gallons
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#7
Quote from stufine View Post :
Cold Water Temp = 45 degrees Fahrenheit
Hot Water Temp = 135 degrees Fahrenheit
Hot Water Tank Volume = 80 gallons
Tank Pre Pressure = 70 PSI
UCPW System Water Pressure = 70 PSI
Maximum Allowable Pressure in Plumbing = 100 PSI

Press "Calculate" and the results display:
Minimum Thermal Expansion Tank Size = 4.46 Gallons
Thank for pointing to tank size estimation.
I checked watts website and based on the numbers it seems what I have is adequate. (attached pic).

By the way, following your lead, I reduced the temperature on the water heater and will check tomorrow morning whether the pressure variation comes down.
If it proves water heater is contributing, I still don't know what is wrong with current expansion tank. tests show is not broken. Frown
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#8
I still question the input pressure, even if the PRV is rated 300.
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#9
Quote from stufine View Post :
I still question the input pressure, even if the PRV is rated 300.
high Input pressure is something we put up with. We complained, had council meetings with township water dept, but they would not do anything to reduce it though people spend thousands on repairs.
By the way, I reduced the hot water temp last night, this morning the high pressure came down to 75 from 80. which means hot water heater is the culprit here. but why expansion tank is not compensating, I am not. It did it until few days ago. Called Watts and they say the tank size I have is right. could not help identify the issue.
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#10
Can't you just adjust the shutoff valve coming into your house to back off the pressure? As far as I know the pressure for your water is a function of your distance from the tower. Are you really close?
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#11
LOL a house I rented once has issues with incoming water pressure >120psi and it was making horrible sounds so loud that you could actually hear them 8 houses down. At least that landlord got stuff fixed fast... no expansion tank just a PRV. Fun when you can't flush to toilet without waking the dead.
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Last edited by jkee May 23, 2016 at 02:09 PM
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#12
Quote from dealgate View Post :
Can't you just adjust the shutoff valve coming into your house to back off the pressure? As far as I know the pressure for your water is a function of your distance from the tower. Are you really close?
Not heard that option, not sure you can precisely control pressure that way. Township guy comes opens/closes, not in my control.
Water tank is not far and it is a hilly area, my neighborhood is on the downhill
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#13
Ive worked in water for quite a few years and I cringe when we have a leak at one of our 4 or so spots that are 95psi. It is quite a mess. The valve by your meter( called a curbstop) wont help you any. Turning it will only reduce your volume and not your actualy pressure. I cant see how the city can allow that much pressure into the homes. If I remember correctly when taking my distribution license test the max pressure is supposed to be 100. I would be curious as to what DEP would say about them sending you guys that much pressure. Being close to the tank wouldn't always equate to high pressure. It takes 2.14 feet of water to get 1psi and most tanks arnt very tall. Most of our tanks give you about 62-66 psi at the bottom of the tower. What city are you in? I will talk to a few people at work tomorrow and see what they say about it. And it wouldn't be very hard to control the pressure going to the system or well it shouldn't be to hard. There are PRVs in our system that control the pressure and keep it at what it should be, but they are probably pretty expensive. Please PM me and I will try to get you some help tomorrow. Let me know if there is anything else I can do or if you have any other questions.
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#14
going by the pressure on your relief valve your tank size is correct. If you had a lower one....

I'm down to 2 things
PRV
something with the tank. But no leaks and holding pressure when empty kinda kills that
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#15
Quote from liftedpsd2010 View Post :
Ive worked in water for quite a few years and I cringe when we have a leak at one of our 4 or so spots that are 95psi. It is quite a mess. The valve by your meter( called a curbstop) wont help you any. Turning it will only reduce your volume and not your actualy pressure. I cant see how the city can allow that much pressure into the homes. If I remember correctly when taking my distribution license test the max pressure is supposed to be 100. I would be curious as to what DEP would say about them sending you guys that much pressure.
In the case of the house I rented, it was a fairly old house and didn't have a PRV at all. It was a fairly sudden event, so something must have gone wrong somewhere upstream. I have to figure either a lot of the neighbors added PRVs previously or something about the way the water mains ran sent more pressure to that house. Trust me you don't want to hear the resonant frequency of your plumbing, I never imagined water pipes could make such loud and awful moaning sounds. That's in addition to the loud thuds that sounded like a car backfiring from outside the house. The landlord got it fixed within 72 hours, but we still got a visit from a noise enforcement officer before then.

Good luck OP, definitely contact your water provider and maybe your local government to complain.
Quote from stufine View Post :
going by the pressure on your relief valve your tank size is correct. If you had a lower one....

I'm down to 2 things
PRV
something with the tank. But no leaks and holding pressure when empty kinda kills that
I think it's probably a matter of the incoming water pressure fluctuating and maybe being in excess of what the PRV was designed for,but there could be something wrong with the valve.

I've lived other places with 70-80 psi without issues to speak of, some water hammer with fast closing valves on sprinklers and washing machines but nothing too alarming.
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Last edited by jkee May 23, 2016 at 07:30 PM
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