Rising pressure...

john p_2

Last night I repaired a die electric union on my buffer tank. I isolated the tank, drained the water into clean tanks so I could reuse the treated water, which I did.
After pumping the water from the tanks back into the buffer tank now I have alot of air in the system and cannot seem to control the pressure on it. I woke up to 25 psi on the gauge and water leaking from the back flow preventer.
I turned the system off and drained waterfrom the 2nd floor zone to lower the pressure but I hear a lot of air in the water circulating in the pipes as well as the automatic vents venting.
My question is which part needs to be replaced, pressure reducing valve, back flow or expansion tank? And secondly, do I shut it down and purge & vent each zone to get rid of all the air? I was reluctant to do that trying to keep the treated water and not introduce all new water.

Jamie Hall

If you have air left in the system you won't be able to control the pressure; replacing parts isn't going to help. You need to purge and bleed each zone separately to get rid of the air -- and you will lose the treated water. Can't help that.

Then when you start bringing it back into action, check the precharge on the expansion tank (isolate it, empty it of water, and check the pressure at the Schrader valve -- it should be set to the cold system pressure. If your backflow preventer still drips from the vent, it will either need to be repaired (some can be) or replaced. If the PRV won't hold pressure, it may need to be replaced. But -- don't do any of that until you get rid of all the air and can see what's really happening.

john p_2

Jamie, thanks. I just vented & purged all zones. Just started the system, all zones calling and hear no air at all. System is set for 18# and so far is staying there. I didn't see your response till after turning on the boiler so I'll check the expansion tank after. Thanks for responding.

Jamie Hall

john p_2 said:

Jamie, thanks. I just vented & purged all zones. Just started the system, all zones calling and hear no air at all. System is set for 18# and so far is staying there. I didn't see your response till after turning on the boiler so I'll check the expansion tank after. Thanks for responding.

If it's holding pressure properly the expansion tank is probably fine. Sit back and enjoy.

john p_2

Running for about two hours @18# with calls for heat. Seems all good now. Thanks again