Initial high water pressure

[Daac]

Hello everyone.
Recently I've noticed that when I turn on the water in my house hot or cold the pressure is initially high for about five seconds or so then drops back down to normal. I bought a pressure gauge and screwed it onto the hot water side of the washing machine hose bib. My house pressure is about 50 psi and about 45 psi when using water. After I use hot water the pressure gauge slowly rises to 80 psi. If I open the hot or cold water pressure drops back down to normal and remains steady. If I turn the hot water tank off and use hot water afterwards the pressure remains at 50. I've searched many forums and the consensus seems to be to install an expansion tank. My issue with this is I have never had this problem before it just started happening. About six years ago I had a new hot water tank and PRV valve installed in the house and no issues until now.
Any help would be appreciated before I start making changes.

 

[frodo]

it is not a expansion tank. that seems to be the "fad" here lately

it is your PRV.

was your prv installed so you can observe the pressure on both sides of it ?

incoming will be high and out will be the low

replace the prv,,,this time, buy a WATTS prv and you wont have to change it again in 8 years

 

[Daac]

There is no where to connect before the PRV to check the pressure.
I do not have the issue with the hot water tank turned off so how can that be the PRV when it's happening due to thermal expansion? Does the PRV allow pressure above it's setpoint to push back out to city water?

 

[KULTULZ]

If I turn the hot water tank off and use hot water afterwards the pressure remains at 50. I've searched many forums and the consensus seems to be to install an expansion tank. My issue with this is I have never had this problem before it just started happening.

You need the expansion tank IMO . The PRV may or may not have a check valve or the city may have installed a new meter w/ check valve preventing the thermal expansion event from returning to municipals water.

 

[Daac]

My PRV is a watts 25aub z3. It seems like an expansion tank is the way to go but why now? I haven't had this issue in seven years. Is there any failure of the hot water tank or PRV that could cause this to happen?

 

[KULTULZ]

Series 25AUB-Z3 Water Pressure Reducing Valves

...are designed to reduce incoming water pressure to a sensible level to protect plumbing system components and reduce water consumption. This series is suitable for water supply pressures up to 300psi (20.7 bar) and may be adjusted from 25 – 75psi (172 – 517 kPa).

The standard setting is 50psi (345 kPa). All parts are quickly and easily serviceable without removing the valve from the line.

The standard bypass feature permits the flow of water back through the valve into the main when pressures, due to thermal expansion on the outlet side of the valve, exceed the pressure in the main supply.

SOURCE- http://media.wattswater.com/ES-25AUB.pdf

One of two-

The water supplier recently changed the meter to include a check valve (call to ask), or

frodo is correct (as usual) and the bypass feature of the PRV is defective.

 

[KULTULZ]

...hmm...

The standard bypass feature permits the flow of water back through the valve into the main when pressures, due to thermal expansion on the outlet side of the valve, exceed the pressure in the main supply.

If your T&P valve ( NOT TPRV! ) discharges @ 150PSI (or below- graduated opening) and the water pressure reducing valve has a flow back provision (no check valve), and supply pressure before the WPRV is above the thermal expansion event pressure, the thermal expansion has nowhere to go but out of the WH T&P valve. TET (thermal expansion tank) is the only option other than a simple pressure release valve plumbed into the circuit with correct drainage. The PRV would be rated at less pressure so it would open before the T&P.

Another thought is any repair done recently (toilet fill valve for instance) has made the system tighter whereas a previous slow pressure leak does not longer occur.

 

[Daac]

The last thing I did was remove a little plastic bushing that gives you slow flow at your faucet. Since then I put it back in no change.
That cut-and-paste about my PRV says the bypass feature allows the flow back only if the pressure in your house is higher than the pressure before the PRV. I will have to check pressure before the PRV I know the strata complex has a PRV but not sure what it set up as. I'm going to suck it up and go get a new PRV throw it in because it's the easiest and cheapest thing to do and see if it makes a change if not there's something wrong with the hot water tank or I need an expansion tank for some reason. Thanks for all the help I will update when I have more information.

 

[Mr_David]

The last thing I did was remove a little plastic bushing that gives you slow flow at your faucet. Since then I put it back in no change.
That cut-and-paste about my PRV says the bypass feature allows the flow back only if the pressure in your house is higher than the pressure before the PRV. I will have to check pressure before the PRV I know the strata complex has a PRV but not sure what it set up as. I'm going to suck it up and go get a new PRV throw it in because it's the easiest and cheapest thing to do and see if it makes a change if not there's something wrong with the hot water tank or I need an expansion tank for some reason. Thanks for all the help I will update when I have more information.

I was about to add my 2 cents and you injected it already.
That is correct about the bypass. Thermal expansion will only pass back into the supply if it exceeds the supply pressure.

Sometimes a toilet ballcock will relieve normal thermal expansion.
The newer fill valves use a lever and diaphragm which uses the water pressure to close the valve unlike old long arm float ballcocks that used the lever action of the float pushing on a seal against the water pressure. Thermal expansion would push the ballcock open just enough to relieve the excess pressure.

So IF you have recently replaced a toilet or toilet fill valve,
that might be why the recent change in thermal expansion now being noticeable.

If you put a gauge on the water system, water heater gas/electric is off
and your pressure does not increase with all fixtures closed ( If you can, turn off stops to toilets and R.O. water filters systems ) then your PRV is holding.
Another thing you can do, IF you have a good service ball valve is turn it off to the house.
Your pressure should hold if you have no leaks.
To make sure your valve does not leak by, let out about 10 psi and see if it holds again.
If it climbs back up, then your valve is leaking by a little.
But if it stops at the set prv pressure, then the prv is working.
Now go and turn on the water heater and let it cook.
If the pressure star to rise on the gauge, then it is thermal expansion.

As a professional, If I'm going to sell someone a prv to fix their problem, I need to be right on.
You would be pissed if it wasn't the PRV and you needed an expansion tank instead.

I was watching the World Series Game 7.
When Lester started pitching I had to walk out.
To many wild pitches in the dirt.

Gonna go back and finish the game. Chapman's coming in to close it.

 

[Mr_David]

OH Crap!!! He gave up 2 runs and tied it up.

Now a rain delay!!! Gonna be long night for somebody