High pressure and Expansion tank

[Modrob]

We live in a rural area but are served with “city water”. Recently they changed out meter (about 150 feet downhill) and a new regulating valve at the meter. Even before this, we had high pressure, and now it’s even higher—fluctuating between 100-120 psi. Hot water tank (I think 30 or 40 gallon) installed about 3 years ago, and I added an expansion tank a little more than a year ago. (I think I have about 35 psi in the ETank because I was afraid to try and push in an amount equal to or more than our pressure!)
Water company says don’t worry—shouldn’t cause any problems. I’m thinking I should install another regulating valve inside the house and get that pressure down…(I’m measuring pressure with a screw-on gauge on the water tank drain bibb)
Thanks much for thoughts.
Tim in WV

 

[John Gayewski]

Yes you need a max of 80 on your house. Get another regulator. Though double regulation can have issues if not done correctly. I would call caleffi and ask them which product you need.

 

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[Reach4]

You should raise the air precharge in your pressure tank to the pressure that your regulator is set for. Always check and set the air precharge with the water pressure zero. Setting the air pressure too low will result in higher expansion pressures than you would otherwise get. Everybody will agree on that.

If your pressure rises like that only after you used much hot water, and have stopped using water, 120 itself is nothing to worry about. As soon as you use a bit of water, the pressure should drop.

This is a rare area of disagreement with John. While many agree that the thermal expansion should not increase the PSI to over 80, I disagree.

My argument is that the thermal expansion tank makers recommendations result in pressures over 100. Some argue that the codes say that the water pressure should not be above 80 psi, and do not state an exception.. And I argue that if we consider 80 psi to be a hard limit, then the great majority of thermal expansion tanks are undersized.

https://terrylove.com/forums/index....g-regulator-question.94022/page-2#post-677156 has my thoughts about there not being a problem for a tank WH if the thermal expansion results in a 100 or even 120 psi for a bit. If you designed

If you had incoming water at 70 psi, and if you were determined to not have the pressure rise over 80 after a hot shower in Minnesota, the thermal expansion tank would have to be much bigger than normal.

Examine that Watts calculator at https://tools.watts.com/ETP/
Look at https://www.amtrol.com/wp-content/uploads/2019/06/9017-112-03_19-MC10007-Sizing-TXT.pdf

150 PSI in the WH tank will not damage the tank, but you don't want the T&P valve to be discharging regularly. So make sure that the pressure never approaches 150.

 

[Modrob]

Wow! I’m still confused…(thanks much for the info so far)
Let me add one other detail that might affect the situation—the water line coming into the tank is 3/8” copper. (my wife’s late husband plumbed the house during building, while on well water—his thoughts were that a smaller supply would keep the kids from taking too long showers LOL)
When I installed the new water heater about 3 years ago, I added in the expansion tank, just because I’d read so many things about it being a good idea. Wife said without one had never been any issues with plumbing so far, other than the previous tank getting a leak around the bottom…
At the time of install, I couldn’t get anything to pump more than about 35-40 psi in it, figuring I’d dig deeper into it later…
When I screwed on that gauge at the tank drain I was shocked to see that pressure staying so high. It reads past the printed numbers—I’d guess it would be in the area of 130 or so. I can turn on a hot spigot for about 30 seconds and it will drop down to about 80-90 but will rise again within a minute or so…
I’m just worried about it getting worse—I believe it has over time…

 

[John Gayewski]

There's nothing confusing. You need a regulator. I understand why you could be confused, but there's a bottom line here. 80 is too high, no manufacturer will tell you different.

 

[Reach4]

1. If your water pressure after your PRV (pressure regulating valve) is 80 or higher while you are dribbling water, the PRV is not working right.

2. If you dribble water, and turn off the WH, then stop dribbling water, the water pressure should stay under 80. If it rises higher, then your PRV is bad.


3. (the one that many will disagree with) If the pressure rises only while the WH is heating, I don't think there is necessarily a problem unless your pressure rises above 132. With that symptom, it is probable that your thermal expansion tank has failed or is undersized.

 

[Fitter30]

Well or city water?

 

[Modrob]

Well or city water?

City water. I talked with the crew last year that was working on the meter and they told me the pressure has always been high, and then they installed a new regulator valve there at the meter. (Coming from Nashville/Chattanooga for over 30 years, this was the first time I’d seen that—I always had a regulator valve installed under my house. Again, our line is in a rural area—in 2017 it came across a small hill/mountain to supply our house and two others nearby. It junctioned alongside the secondary one-lane road, and our meter was put in on the other side of the road. Then we put in the line from there about 150 feet uphill to the house…
The crew didn’t seem to have an issue with readings of about 110–120 psi at that time…
I will go today and get a regulator and install it ASAP…this thing is worrying me as tonight the gauge is reading even higher…

 

[Fitter30]

Expansion tank air charge needs to be the same as the regulator. If pressure is 60# after new reg. Valve system off drain it down adjust air charge with a tire gauge and bike air pump. Open system slowly.

 

[Modrob]

Thanks to all of you for helping. Yesterday I installed a pressure reducing valve and adjusted to 70psi. But I could not get the expansion tank to accept any air, nor expel any if I removed the valve stem. I finally removed it, but found it was nearly full of water. (Could it be the constant high pressure destroyed the bladder?)
So, now we’re back to nearly the beginning, only now with the PRV in place. And all appears fine…
Quite happy now and relieved…thanks again to all.

 

[Reach4]

You need to replace the thermal expansion tank. If you doubt that, put a container under the output of the WH temperature and pressure relief valve output. There should be no water coming out of that, even after a hot shower.

 

[Jeff H Young]

The regulator was bad or mal adjusted as was/ is expansion tank.

 

[Modrob]

So far…
Still maintaining a constant 70psi, and all water fixtures performing well. @Reach4 and not a drop from the relief valve so far….
Out of curiosity yesterday I took the 2.5 gal expansion tank to the bench—still would not accept any air fed into it. Took out the valve stem and still nothing in or out. Looked inside from the bottom and could see the bladder down near or at the top of the tank. Flipped it back over and stuck a blunt object down the air valve—it would barely go in. It’s as if the bladder part is stuck or solidified, and won’t move at all…figuring I had nothing to lose I sprayed PB Blaster down the water side and swished all around the outside edge…no difference…
Shouldn’t that bladder move and accept some air, even sitting on the bench?

 

[Reach4]

Weird occurrence. Yes, with the valve core removed, the tank should take air.

 

[Fitter30]

Yes the bladder should take air my money is the bladder is compromised.

 

[Michael Young]

We live in a rural area but are served with “city water”. Recently they changed out meter (about 150 feet downhill) and a new regulating valve at the meter. Even before this, we had high pressure, and now it’s even higher—fluctuating between 100-120 psi. Hot water tank (I think 30 or 40 gallon) installed about 3 years ago, and I added an expansion tank a little more than a year ago. (I think I have about 35 psi in the ETank because I was afraid to try and push in an amount equal to or more than our pressure!)
Water company says don’t worry—shouldn’t cause any problems. I’m thinking I should install another regulating valve inside the house and get that pressure down…(I’m measuring pressure with a screw-on gauge on the water tank drain bibb)
Thanks much for thoughts.
Tim in WV

Get that pressure to between 60-80psi. DO NOT go higher than 80-psi (per code). Manufacturers look at the code as their minimum standard. EVERY SINGLE FIXTURE in your house is built to handle 80-psi. Once you go past 80, you have no warranty on anything in your house.