Pressure reducing regulator question...

[Brian Ferri]

I've noticed low water pressure for days while the city flushed out the hydrants. When they finished, the pressure seemed high so I bought a pressure meter and it registered 110psi. I lowered the psi to 50 by adjusting the regulator by the main shut off. But now that I have the meter still connected I've been monitoring it and noticed at times the red meter hand will reflect the psi shot up to 90 or about, while the black hand was at 50.

So, I think the hot water heater kicking on creates that high psi reflected by the red hand, and at some point psi returns to 50 reflected byb the black hand.

Should I be concerned? If i didn't have this meter I wouldn't know any of this.
Is this normal?

Thanks

 

[Reach4]

Should I be concerned?

No.
That is due to thermal expansion when you use hot water, and the new cold water gets heated.

I would not worry about 130 in that case. There are some that would find that worrisome, but you really you don't want the pressure to rise to the level where the temperature and pressure valve would have to open (nominal 150 psi).

 

[Sponsor]

 

[Brian Ferri]

No.
That is due to thermal expansion when you use hot water, and the new cold water gets heated.

Thank you! That's a relief!

 

[Terry]

Most codes like to see the pressure at 80 PSI or less.
How old is your PRV?

 

[Brian Ferri]

It's about 8 years old...

 

[Terry]

It's about 8 years old...

Fairly new then.

 

[Brian Ferri]

How long should they last?

Thanks for your response Terry...

 

[Reach4]

I think the codes accept higher pressures due to thermal expansion.
http://tools.watts.com/ETP/ If somebody puts in some test data into the calculators, they will see that the calculators assume that higher pressures are fully acceptable.

If pressures of 90 due to thermal expansion were actually forbidden, the thermal expansion tanks would have to be much better.

 

[Michael Young]

No.
That is due to thermal expansion when you use hot water, and the new cold water gets heated.

I would not worry about 130 in that case. There are some that would find that worrisome, but you really you don't want the pressure to rise to the level where the temperature and pressure valve would have to open (nominal 150 psi).

80 psi is the proper (code) setting for your PRV
if you're getting fluctuations, it shouldn't be from the supply side. Your PRV should keep your pressure at 80psi
on the house side of the PRV, if you're getting fluctuations, you need to add a thermal expansion tank
and READ THE DIRECTIONS on the tank. You need to pressurize the expansion tank. Yes, the expansion tanks do come pre-pressurized. But they do not come CALIBRATED to your particular need.

-Mike
https://homeservicestriad.com/

 

[Brian Ferri]

So, is this still fine? Seems high...

Do I need to disconnect the meter and stop thinking about it?

 

[Reach4]

So, is this still fine? Seems high...

Do I need to disconnect the meter and stop thinking about it?

Yes, fine. If it gets to 130, put in a bigger thermal expansion tank. Disconnecting the meter is fine too, since you are unlikely to be climbing beyond 13o.

One thing... those lazy (tattletale) hands can be affected by vibration. If you tap the gauge, you can see that red hand jump.

 

[Brian Ferri]

You mean the thermal expansion tank by the hot water heater?

 

[Reach4]

You mean the thermal expansion tank by the hot water heater?

Yes. That is the thing that keeps the water pressure from opening the WH T&P relief valve, by absorbing the expanded water.

 

[Brian Ferri]

Thank you!

 

[Brian Ferri]

Yes, fine. If it gets to 130, put in a bigger thermal expansion tank. Disconnecting the meter is fine too, since you are unlikely to be climbing beyond 13o.

One thing... those lazy (tattletale) hands can be affected by vibration. If you tap the gauge, you can see that red hand jump.

This is where I get anal, my technical side.

I thought most plumbing fixtures are rated for about 50 psi, not sure what pex is rated for. But after a shower psi shoots to 110 or so and that pressure appears to stay until someone opens a faucet for whatever reason. Shouldn't there be another way to relieve that pressure? Is there? Maybe a leaking pipe would relieve it but knock on wood, don't think we have one.

 

[Reach4]

This is where I get anal, my technical side.

I thought most plumbing fixtures are rated for about 50 psi, not sure what pex is rated for. But after a shower psi shoots to 110 or so and that pressure appears to stay until someone opens a faucet for whatever reason. Shouldn't there be another way to relieve that pressure? Is there? Maybe a leaking pipe would relieve it but knock on wood, don't think we have one.

1. How technical? Look up the thermal expansion of water with temperature. Figure your 50 gallon WH. Assume the water temperature rises by 30F while the system is closed? How much does the water volume increase?

2. Note when you turn on that water faucet even a tiny bit, the pressure drops almost instantly.

3. There is another system where there is a pressure relief valve that lets off the extra pressure at maybe 130. That works, but it takes some water. That is undesirable in drought. Letting the water expand into a thermal expansion tank gives that water back for use. There used to be a toilet fill valve that combined a pressure release to limit the pressure.

 

[Brian Ferri]

You win, that's above my head, lol.

Thanks for your explanations though...

 

[Jadnashua]

If your expansion tank is sized properly and the precharge is correct, your pressure should NOT spike that high. Since water isn't compressible, any expansion will raise the pressure unless there's some place for that water to go...that could be something that leaks at pressure, a valve that has a slow leak, the flex hoses expanding on things like your washing machine, toilet, or faucets. Those expansion/contraction age things, so trying to minimize it is a good idea.

To test the precharge pressure in your expansion tank, shut the water off, open a valve to relieve any pressure, then using a tire pressure gauge, check the pressure in the ET. It should be set to the same pressure as your PRV is set to. Then, any expansion has the maximum room in the tank. If, when you check the air pressure with the tire pressure gauge, you get some water out, the tank is shot...replace it.

To verify that it's sized properly, there are calculators online you can use. You need a few things, and you can estimate if you don't know the exact answer. You'll need to know:
- size of the WH
- incoming normal water temperature
- normal operating temperature of the WH
then, the calculator will determine the size ET you should have. A larger one is fine, smaller is not good.

 

[Brian Ferri]

Thank you for the feedback!

 

[Reach4]

If your expansion tank is sized properly and the precharge is correct, your pressure should NOT spike that high.

Brian, understand that I think jadnashua is persistently misguided on this.