To Much Pressure in Water Heater?

[disney1984]

I have a 50 Gallon State water heater attached to hydronic heating system in my home attic. I had the water heater professionally installed by a plumber about 5 years ago. The unit had a problem with the 150 PSI tp valve blowing immediately after the installation. The plumber was frustrated and confused at why it was blowing. He added an expansion tank just to be safe. He also installed another new tp valve and its worked fine for 5 years. About six months ago I noticed the tp valve blowing again. I've had a couple of plumbers come out and they can't figure out what the problem is. They checked the expansion tank and it isn't full of water and appears to be OK. I performed my own investigation. Water pressure at a hose bib outside of the house is a constant 60-65 PSI. I placed a pressure gauge on the water heater at the drain bib as well. I discovered that pressure at the water heater bib would reach 140 PSI towards the end of the water being heated after someone took a shower right before the burner would kick down. The 140 PSI slowly drops after the burner turns down. The PSI at the outside hose bib remained a constant 60-65 PSI. The tp valve starts leaking a small, but steady stream at 140 PSI. It's obvious to me that the tp valve is bad because it shouldn't blow until 150 PSI, but I'm being told the internal pressure of the water heater should never get that high. I called the Tech line at State Water Heaters and told them of my problem. The temperature setting on the water heater isn't to hot and is set at 120 degrees. It was at 125 degrees. State says the internal pressure of the water heater shouldn't get over 80 PSI. The pressure gets to 140 PSI without the hydronic house heater being on. 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 a about 3 weeks and the problem has started up again. Should the internal pressure of the water heater get up to 140 PSI? The manufacturer says no. Does anyone have any idea what could be going on here?

 

[Twowaxhack]

Sounds like you have a check valve between the water heater and your hose bibbs outside and your thermal expansion tank isn’t working.

It either is not set to the proper pressure or it’s failed.

 

[disney1984]

I really appreciate your response Twowaxhack. I'm not a plumber, but I fix a lot of things around my home and I'm technically inclined. I've avoided working on my water heater in the past because of potential safety issues, but I can't seem to get answers on what the problem is from my local plumbers, and they keep charging me to just look at the unit.

My home is about 25 years old, and the builder designed it with an Apollo hydronic system. My home was built with a 50-gallon State water heater, and it worked great for 20 years until it started leaking. The two hydronic lines come off the side of the water heater. It's been like that since day 1 and its always worked out fine. The replacement State water heater installed 5 years ago is almost identical to the original, but its ultra-low NOx.

The last plumber that came out was in his 20's and seemed a little inexperienced. He checked my expansion tank and said it was fine. I decided to check it myself last night and it was extremely heavy. I'm concluding that it must be filled with water because it fills so heavy. This is evidence of a failed expansion tank, right? Could this be the reason the internal pressure of the water heater is reaching 140 PSI at times?

 

[disney1984]

I think this is a one-way check valve that's in-line on the water supply to the water heater. The plumber that installed my current water heater added it. It wasn't there when I took possession of the house. I would expect to see an arrow pointing one direction, but I don't see any. I don't have enough experience with these. Is this a one-way check valve and could it be contributing to the problem? Thanks in advance.

 

[Twowaxhack]

First off let me tell you that I do not work on hydronic systems. We simply don’t have them here.

Yes, it seems your expansion tank has failed or it wasn’t properly pressurized with the air charge.

 

[Twowaxhack]

That appears to be a check valve to me. Spring type.

 

[wpns]

Classic symptoms of a failed expansion tank.

 

[hdtvkeith]

Does he even have an expansion tank, my home was built in 1984 and they did not use expansion tanks back then as the municipal water did not have any back flow preventers. About 15 years ago they came through told every to get expansion tanks installed as they were going to be putting back flow preventers. I only have a 50 gallon tank but went with 4.5gallon expansion tanks to be safe.

 

[RS]

It sounds to me like your expansion tank is waterlogged, try adding some air to it. If that solves your problem then it's the culprit. Just adding some air occasionally will get you by.

 

[hpp8140]

I am not a professional, just a handy homeowner with Apollo hydronic heat. I had an issue where my TP valve opened and set off the water alarm. Troubleshooting led me to the expansion tank heavy filled with water. You can try to test it by releasing air from the valve, like a tire...it should not have water coming out. Water may not come out, but it may have developed a hole in the diaphram. DO NOT pump air into the expansion tank while installed.

 

[Twowaxhack]

I am not a professional, just a handy homeowner with Apollo hydronic heat. I had an issue where my TP valve opened and set off the water alarm. Troubleshooting led me to the expansion tank heavy filled with water. You can try to test it by releasing air from the valve, like a tire...it should not have water coming out. Water may not come out, but it may have developed a hole in the diaphram. DO NOT pump air into the expansion tank while installed.

You can pump air into the tank with it installed but you need to turn the water off and relieve the pressure on the system.

 

[disney1984]

I depressed the Shrader valve on the expansion tank last night and nothing came out. Neither water nor air. The tank is still extremely heavy and I'm feeling confident the tank has failed. 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.

 

[disney1984]

Here's a photo of my expansion tank and the piping at the top of my water heater.

 

[wpns]

Yes, that should work fine, though I think you should have the precharge slightly higher than your normal house pressure, so the tank capacity starts to be used when the hot water heater is overpressurising the house.

 

[RS]

I would just air it up and see what happens, it might be fine for years!

 

[Twowaxhack]

Yes, that should work fine, though I think you should have the precharge slightly higher than your normal house pressure, so the tank capacity starts to be used when the hot water heater is overpressurising the house.

You can go up to approximately 80 psi and that’s it or you’ll be over max psi for the house. This also reduces the expansion tanks capacity to control thermal expansion. That may or may not be of concern, usually it’s ok and the tanks big enough anyway.

 

[Twowaxhack]

I can’t exactly tell if the expansion tank is on the proper side of the check valve. It may be but I’m not positive.

 

[disney1984]

I appreciate all of your advice. The water line feeding into the water heater goes through a gate valve, then what appears to be a one way check valve, then into a tee fitting on the top of the tank, which the expansion tank line goes into the top of. You can see a small copper line going up on the water feed line next to the gate valve. It goes nowhere and is capped off. Its only about six inches long. That may be throwing you off. I have no idea why the plumber did it that way. Maybe he improvised because of limited parts on his truck.

 

[hpp8140]

Make sure to size the expansion tank correctly to your water heater, also have a large bucket ready when you remove it in case it's filled and heavy

 

[disney1984]

I changed out the expansion tank about 3 weeks ago and everything is working perfectly now. The T & P valve is no longer releasing water and the internal water heater pressure doesn't go much higher than the incoming water pressure. The old expansion tank was completely full of water. I'm not a professional plumber and couldn't have done it without everyone's assistance! Thank you so much for your help!