Problems after pipe replacement

TMK

I recently replaced some leaking pipes on my old one-pipe steam heat system, and now I have a strange problem: one stack heats fine, the other doesn't.

I assumed it was a problem with too much air in the systems, so I closed all the valves on the heating stack, and turned the thermostat up quite high. Then, on the non-heating stack, I removed several radiators and opened the valves, which usually purges the system almost instantaneously. Now, hours later, while I can still hear some gurgling, there is very little air movement, and definitely no steam.

Any ideas?

Abracadabra

Was boiler skimmed after the new pipes were replaced?
Was pitch maintained on the pipes that were changed?

TMK

Thanks - I will double check that, although I am pretty sure the pitch is good.

Jamie Hall

Er... Removed several radiators and opened the valves? Say again? Just as well that there is something amiss -- that's a recipe for serious burns on a steam system.

First, off, all the valves on a one pipe steam should always be fully open. Second, turning the thermostat up quite high doesn't change anything; either the boiler is running or it's not. Third, a steam system is always full of air when the boiler isn't running. The purpose of the vents on the mains and the radiators is to let the air out when the boiler fires up.

All that said, steam can't go where there is either water trapped or the air can't get out. Since this happened after you changed some pipes, I would go over all the pipes to make absolutely sure that there is nowhere that water can be trapped, for starters.

Fred

I assume the pipes that leaked and were replaced were wet returns (below the boiler's water line? If so, did you keep them that way or did you make some changes that might now put those returns above the water line? Pictures of the boiler and piping would help.

Jamie Hall

Fred said:

I assume the pipes that leaked and were replaced were wet returns (below the boiler's water line? If so, did you keep them that way or did you make some changes that might now put those returns above the water line? Pictures of the boiler and piping would help.

Hadn't thought of that possibility. Never underestimate the opposition... if that has happened, that could cause huge problems -- including the ones the OP describes.

TMK

Fred said:

I assume the pipes that leaked and were replaced were wet returns (below the boiler's water line? If so, did you keep them that way or did you make some changes that might now put those returns above the water line? Pictures of the boiler and piping would help.

They new pipes sit a little higher - two inches - than the previous pipes, as they were in fact rusted from the outside by being on the ground... but I'm pretty sure are still below the waterline (the boiler sits on a large concrete block, elevating it by nearly half a foot. I will try to take some pics tomorrow. Thanks so much!