Expansion tank issues

[Shaggy76078]

Been running through relief valves on our 50 gallon a&o smith water heater. When we got this one it was recommended to add an expansion tank. Did that. Went through another pressure valve just 2 days ago. After hooking up my pressure gauge to a faucet, shows 120-130 psi coming from the road, expansion tank says max 80psi. I know ive read that the expansion tank psi should equal incoming pressure. Do i need a bigger, higher pressure expansion tank, do i need to lower the pressure on the shut off at the rd to 70-80 psi, do i need a prv at the water heater? Not sure where to go next on this as ive always done water heater replacements and never had an expansion tank added on ever.

 

[Slomoola]

House water pressure should be 40-60psi, 80psi MAX. Anything over 80 needs a PRV.

 

[Sponsor]

 

[GReynolds929]

Max is 80 therefore anything over 80 requires a PRV. Are you really installing unnecessary PRV's for people! I set the PRV's I install to 65.

 

[GReynolds929]

Been running through relief valves on our 50 gallon a&o smith water heater. When we got this one it was recommended to add an expansion tank. Did that. Went through another pressure valve just 2 days ago. After hooking up my pressure gauge to a faucet, shows 120-130 psi coming from the road, expansion tank says max 80psi. I know ive read that the expansion tank psi should equal incoming pressure. Do i need a bigger, higher pressure expansion tank, do i need to lower the pressure on the shut off at the rd to 70-80 psi, do i need a prv at the water heater? Not sure where to go next on this as ive always done water heater replacements and never had an expansion tank added on ever.

You need a PRV on your main before it branches to other fixtures in the house.

 

[SAS]

I think there may be some confusion here between pressure relief valves and pressure reducing valves (or at least I'm confused by what you are saying). Normally you would have a pressure reducing valve near the water meter. That would reduce the pressure throughout your house from 120-130 psi (which is too high for most residential plumbing systems - including your water heater) to something in the range of about 60 psi. Here's what they usually look like:

That would reduce the incoming pressure to your water heater to a manageable range. I'll leave it to the real plumbers to judge whether you also need an expansion tank. It's purpose is to absorb the added pressure created in the tank when the water is heated. You would indeed set the pressure in the tank to match the water pressure measured at a faucet, but it should now be around 60 psi.
In my house the pressure reducing valve was malfunctioning, with the pressure varying erratically. I found that I could simply replace the innards of the valve, which was both much less expensive and also did not require any real plumbing work. Once I had that settled at roughly 70 psi, I adjusted the pressure in the expansion tank to 70 psi as well. That's been working fine for a couple of years now.

 

[Fitter30]

City water after prv. Ex tank air charge match the pressure of your water pressure with tank before use. Use either a hand pump or air compressor with very short blasts check pressure after each blast. Don't want to blow the bladder.

 

[John Gayewski]

Any time there's a prv there needs to be an expansion tank. If your prv is letting the pressure creep up then it isn't closing properly and needs cleaned or replaced.

Most houses only need a small expansion tank to handle the volume of expanded hot water. Even with an expansion tank the pressure will creep up when the water is heated. As long as the pressure isn't creeping up above 80 your fine.

You might need to set the prv at 60 and let the pressure creep up to 70 or so from the heater, depends on how much heat and water in is in your system.

Figure out where the high pressure is coming from and fix accordingly. The relief valve is only a tattle tale the ones you've been going through are probably fine.