Hot Water Heat-Pressure Out Of Control!

Jeff_105

We have an older two story house with a hot water heating system. Today I bled the upstairs radiators. After doing this, I noticed that the pressure had gone very low in our system, so I added some water. Now, suddenly, the pressure is really, really high. I have to keep removing water from the overflow tank, but as long as the heat is on the pressure keeps building. It seems endless! What have I done, and what can I do to bring the system back under control?

I believe I have a "closed" system. The overflow tank is just above the furnace.

I'm not a plumber (obviously) and really don't understand what is happening. If anyone can give me some ideas I'd really appreciate it!

TK03

You may not be putting air back into the expansion tank. If you are just putting a drain hose on the connection -you are probably putting water in at the same rate that you are draining it. Turn the supply water off-attach hose and drain tank but be sure air is going back in when its empty. Then turn the supply water back on. The tank should have the air cushion again.

Mark Eatherton

Water logged expansion tank...

Can you take pictures and post them here?

I once worked on a home that had NO expansion tank.

I made the mistake of bleeding all the air out of the large, upright radiators. Next day, HO calls and says there is water all over the floor. Bad relief valve, I sez.

Replace the relief valve. Next day, same call, water all over the floor from NEW relief valve...

Bad make up valve, I sez. Replace make up valve.

Next day HO calls with the same complaint, water all over basement floor from pressure relief valve. Start looking for expansion tank and find none.

Light bulb goes off over head.

Drain system completely, refill system. Do NOT bleed radiators. Problem and customer goes away... Never heard from them since.

Live and learn.

ME

Jeff_105

Thank you for your replies.

There is definitely an expansion tank. Here is my further question.

There are three valves I know about. There is a valve which is what puts water into the system in the first place. There is a valve which I can use to drain from the expansion tank, which I think I'd use to drain the system completely. There is also a third valve connecting the expansion tank to the furnace, which allows water from the furnace piping system into the expansion tank.

When I drain the system completely from the expansion tank, do I shut off the valve from the furnace into the expansion tank, or do I leave it open? Then, when I refill the system, do I shut this valve or keep it open?

If you could give me a step by step procedure, it would help a lot. Thanks again!

Jeff

TK03

procedure

Shut the valve off that puts water into the boiler. It might be a B&G red or gold in color. Shut the valve off leading to the expansion tank. Attach hose onto tank drain and drain tank till it is empty and only air is there. Close the drain. Open the valve to let water into the boiler. Open the valve going to the exp tank. You should hear it filling and it will stop by itself.Pressure should then be ok

Jeff_105

Thanks Jason . . .

I'll try in the morning. If I need more guidance I'll write again.

Are you sure the valve allowing water into the system should remain open? And it will stop by itself?

Please excuse my questions. I'm feeling a bit waterlogged myself right now

Jeff

TK03

Shut it off when draining tank but turn it back on when filling the tank and leave it alone.

Mark Eatherton

ASSUMPTION BEING....

that there is an operational pressure reducing valve on that water line.

Got pictures?

ME

Jeff_105

Waterlogged Expansion Tank . . .

Thank you both, Jason and Mark, for your replies and your help. The system is working now with steady pressure!

I have one more question, if you don't mind. Bleeding our radiators is what seemed to set this pressure problem off. Does bleeding the radiators with the valve to the expansion tank open cause the tank to become waterlogged? Does it draw the air out of the tank?

If so, is the solution to shut off the valve to the expansion tank before bleeding the radiators?

Or is it necessary to drain the expansion tank whenever we bleed the radiators?

Thanks again!

Jeff

Mark Eatherton

Jeff...

You're welcome. Thanks for checking back.
In reality, it shouldn't matte what position the isolation valve to the expansion tank is in. I suspect that your tank was water logged PRIOR to your bleeding the radiators, and then when you bled the radiators, you had no expansion compensation and the pressure problem reared its ugly head.

My presumption is that your expansion tank is a non diaphragm type of tank. If so, and there are ANY automatic air vents on the system you must either get rid of the air vents, or get rid of the non diaphragm tank and replace it with a diaphragm type tank.

Under "good" operating conditions, the free air in the system should be recovered and diverted back to the expansion or "cushion" tank as it is referred to in older literature. On rare occasions, it can lose its air bubble into the system, and if and when that does happen, you have to COMPLETELY drain the expansion tank and let the atmospheric pressure equalize in the tank, then recharge the system pressure which should be 1/2 PSI for each vertical foot of system elevation above the gauge, PLUS 5 PSI (minimum typically 12 PSI)

More information on expansion tanks can be found at

http://www.contractormag.com/articles/columnist.cfm?columnistid=6

Scroll ALL the way down to the bottom to find the articles I've written n expansion tanks.

ME