Too Much Pressure in Water Heater?

[John Gayewski]

From 60 degrees to 125 degrees gets you 65 degrees of temp difference. Say there's 50 gal of water being heated. You gain 1.495 gal. of water. That's gonna cause a pretty big pressure rise without a working expansion tank. Prv or no. It's possible to calculate but very difficult without a lot of specific info. He needs at least a two gallon expansion tank if there's 50 gal of water in this system. I'm guessing there's more.

 

[Terry]

Every water heater I install with a recirc system gets a check valve.
I never have an issue.

Why are all of you opposed to taking a pressure reading on a cold tank?

 

[Sponsor]

 

[wwhitney]

Why are all of you opposed to taking a pressure reading on a cold tank? [/SIZE]

No opposition, and the tank doesn't even have to be cold. As long as it's not firing, and a hot water faucet is opened and closed, the pressure reading should be the supply static pressure.

But that reading should match the hose bib reading (adjusted for height, and up to time variation of the municipal supply pressure), unless as you say there's a PRV in between them. So it's a good way to check for any such PRV.

Cheers, Wayne

 

[John Gayewski]

Every water heater I install with a recirc system gets a check valve.
I never have an issue.

Why are all of you opposed to taking a pressure reading on a cold tank?

Not opposed. I just think if the incoming water pressure was the problem it wouldn't jump down to 65 and back up. He should take as many measurements as possible to get a good idea of what's happening more is better.

 

[Jeff H Young]

I had really answers for this the original provided info I knew was bad, t and p might be weak but the problem was a bad x tank and a check valve had to be somewhere.
Im late to party forgot to send a reply last night you seem to have it handled good luck

 

[Terry]

I must have missed this line.

The weird thing is the water heater pressure recently stopped jumping to 140 PSI and stayed at 65-70 PSI through the heating cycle. It was fine for about 3 weeks

 

[Reach4]

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.

 

[Jeff H Young]

Not opposed. I just think if the incoming water pressure was the problem it wouldn't jump down to 65 and back up. He should take as many measurements as possible to get a good idea of what's happening more is better.

yea those prv's tend to creep in pressure. but is a real simple problem the way to figure it out is to start from scratch ignore all previous info about whats good or bad or the pressure readings take all new ones ignore what plumber said test for himself .

 

[Jadnashua]

Okay, just to clarify, does the WH supply your domestic hot water AND supplies space heating, or is the tank only for space heating?

If the main system's pressure stays stable, it's not a PRV thing, it's expansion.

The PRV essentially acts like a check valve. A second one, unless you have a recirc system, isn't generally required.

 

[Sylvan]

This is illegal in a great many jurisdictions mainly because of the last sentence in your snippet. This is a type of system that should be avoided and is generally frowned upon by professionals even where it legal.

Most code officials have no clue.

If someone is smart enough to pass a masters exam why would they work for chump change working for the government UNLESS they have no ambition

 

[Disney1984]

I've attached a photo of my expansion tank and the piping at the top of my water heater. I'm feeling confident about my expansion tank having failed. The tank is really heavy like its full of water. I depressed the Shrader valve and nothing came out. Not water or air.
Yes, the water pressure at a hose bib outside of the house is a constant 60-65 PSI, even when the pressure at the drain bib on the water heater reaches 140 PSI after heating the water back up after a shower or bath. That tells me the problem is not the City regulated water supply, but is the water heater set-up, right? Do I have what is considered a closed system because of the one-way check valve on the water inlet?

This was mentioned above by Terry:

"Has anyone taken the pressure at the water heater, with the heat turned off?
It may be that the front bib has a reducer on it for irrigation purposes.
In all my years of plumbing, I've never had cold water to a water heater, heated up to 125 degrees ever get over 90 PSI"

The water heater pressure hasn't been recently checked with the burner off, but the problem stopped for a few weeks and the pressure read no more than 80 PSI at the water heater drain bib and the tp valve stopped releasing water. That seemed OK to me. I was confused as to why the problem stopped/started up again. I don't think the bib on the water heater drain has a reducer for this reason.

 

[Disney1984]

I have a smaller 2-gallon tank and I'm thinking of upgrading it to a 4-gallon tank. I've been researching how to replace it myself. I have a gas water heater. This is the process I'm thinking of using to replace the expansion tank. Does it sound right to you?

1) Turn off the water heater and shut off the gas going to it.
2) Shut off all gate valves going to and from the water heater. Water inlet, hot water outlet, hydronic supply and return.
3) Let the unit cool down. 30-60 minutes?
4) Release water out of the tp valve to reduce water pressure still in water heater tank.
5) Remove existing expansion tank.
6) Replace expansion tank bracket to accommodate larger tank.
7) Install the new expansion tank with Teflon tape on the threads. Add additional air pressure to expansion tank to match house water pressure. 62 PSI to match 60-65 PSI house water pressure? What should I set it at?
8) Open the water inlet gate valve and allow for water to re-enter the tank.
9) Check for leaks.
10) Open the rest of the gate valves and restart the burner.

 

[Reach4]

1. I would not shut off the gas. I am not a pro.
4. This would not be a bad time to drain some gallons to be rid of any sediment at the bottom of the tank. That can be done while the WH is pressurized, or not. But if not pressurized, you need to allow air in by opening a hot faucet.

6. You might post a photo of the existing tank area. People may have suggestions.
7. I would think 64 or 65 psi. PTFE tape and pipe dope both is less likely to leak, but either will do the job with enough torque.

 

[wwhitney]

1) Do shut off the gas, you don't want it to fire while you are working.
3) May not be necessary, you could just drain some of the hot water at the bottom (after step 4)
4) Open a hot water fixture to release the pressure.
7) On the flexible connector, any connection to it that has a rubber washer, you don't use teflon tape. But metal threads to metal threads, you use teflon tape.

Cheers, Wayne

 

[Jeff H Young]

Id just turn it down to pilot no need to relight
FYI I have 125 psi outside and 50 inside with a prv no expansion tank and no problems. I should install the X tank but in 20 years havent yet.
Any way good luck no sence talking more if you are going through with a new tank until we know what happens, but do let us know how it works out.

 

[Jeff H Young]

nothing wrong with a checkvalve on the cold inlet for water heater , always install an expansion tank on such systems

 

[Reach4]

Id just turn it down to pilot no need to relight
FYI I have 125 psi outside and 50 inside with a prv no expansion tank and no problems. I should install the X tank but in 20 years havent yet.
Any way good luck no sence talking more if you are going through with a new tank until we know what happens, but do let us know how it works out.

You may have a bypass PRV, and no check valve at the water meter.

 

[John Gayewski]

I would go to your max inlet pressure. If your house bib never goes above 65psi then go 65 psi. You only want water that expanded to go into your expansion tank and then you'd like it to come back out when water is used.

I'm curious about your hydronic system, you should map that out and have someone who really knows what they are doing look at it. This can be unsanitary and unsafe.

 

[Disney1984]

I appreciate all of the advice! I was looking at the flexible tube going to the expansion tank and I was wondering how it was sealing, since I couldn't see any Teflon tape on the existing threads. The rubber washer makes complete sense and now I know how its sealing. Thank you! I plan to set the expansion tank to 65 PSI and thank you for that advice. I was unsure of where to set it, since it varies between 60-65 PSI.

The builder never gave us instructions on maintaining the hydronic system and the plumbers that came out over the years never told us that maintenance should be done. Most of these plumbers had never dealt with a home hydronic heating system.

My hydronic system is definitely on my radar now and I found an experienced local plumbing company that will come out and perform a flush and service it. I'm kind of concerned about it at this point from stuff I'm reading on the Internet and what's being said in this forum. I plan to do this before winter and I'll pay close attention to what they are doing, so I can maybe do it myself in the future. From what they told me, Apollo went out of business a few years ago and no longer makes parts for these units. I was told the Apollo hydronic radiators in the attic usually start leaking after 20 years and customers usually convert to electric after that. I've got about 24-25 years on it now. Not good.

 

[Fitter30]

40 gallon water heater with no ex tank will raise water pressure 4 lbs per degree rise ( Bradford White)
16° rise = 64 lbs