Steam In Return

The way that collection of fittings and pipes is put together is a bit odd — and there must be a good deal more piping. However, given what is shown, the pipe labeled "return" isn't one. It is directly connected to two pipes labeled "steam main" and is thus a steam main or, possible, a "steam main extension".

Can you provide a few more pictures showing a more general view of the boiler and the near boiler piping, and at least one radiator — both ends — and how the radiator steam runout and return lines are connected.

Thank you! I think we are making headway here.

You have — quite correctly — identified the mains and the returns out in the wild so to speak.

That odd petcock thing on the returns where they join did, once upon a time, go to an extractor or maybe even a proper vacuum pump. Don't worry about it. What does need to happen is to have a good big vent or two installed there — probably two Gorton #2s would be appropriate. There will also need to be a vent — another Gorton #2 — on the end of the real steam main before it makes that drop.

Now to the problem of steam in those what we now recognize as returns. As you note, shouldn't be there. The pipe dropping from the end of the steam main is needed — it's the condensate drip from the steam main — BUT it should join those other pipes coming down well below the water line of the boiler, and I'm going to be that if you check you may find that in fact it joins above the water line. That is a much smaller boiler than was in there originally, and the old boiler's water line might easily have been a couple of feet higher.

What happens, I think, is that steam whizzes happily around the steam main — zips down that pipe and then zips right back up again into the return lines. Where it shouldn't be. The simplest and most reliable way to remedy that is going to be some repiping, but not much. Take the two lines which you idebtfued as stean naubs initially, join them together. Drop them all the way to the floor. Take the third line, which comes down from the steam main proper and also drop that to the floor, then join the lot of them together and bring them over to the Hartford Loop and return to the boiler.

You mentioned, by the way, something about an F&T trap. There is no need for such a nuisance…

Oh no. You won't have to scrap it — just a few tweaks here and there will get you good! And your comment on what happens if you raise the boiler water level really makes me think we are on the right track here.

trivial. Of no cosequence.

all of the connections from the mains to the return must be separate for each main and connect below the water line. they can connect to the same return as long as they drop below the water line first. the water prevents the steam from being able to get to the return. in fact the riser from the return likely remains filled with air so steam does not generally get down the riser since there is no place for that air to go because the water in the return is blocking it.

the connections from the dry returns to the wet returns may combine before they go below the water line.

higher differential pressure will push the steam from the mains through the water seal and in to the returns, that among other reasons is why controlling the pressure to a few oz/in^2 with a vaporstat is important.(also if you have radiators with vapor valves and no traps it keeps the steam from blowing through the radiators and in to the returns but you seem to have traps on your radiators).

if someone increased the pressuretrol/vaporstat settings that could cause this to be a new problem.

whoever installed that boiler should have brought those down to near the floor before tying them together. if it is a vapor system there may be some differential pressure control device that is now missing as well although a vaporstat can usually make it work without it.

that isn't a correcting for the new boiler that is just steam piping 101. if there is something out in the system somewhere that was below the water line that no longer is, that is a failure to evaluate the system when replacing the boiler and a consequence of a boiler with a lower water line.

this piping was installed with the new boiler, anyone that knows steam knows they have to drop those below the water line before connecting them together.

Since there are no crossover traps, this way (with 3 main vents) would probably vent the mains as fast as practical. Heat the pipe up with a torch to get that pipe plug out.

Depending on the original system (which most of its interesting parts are probably long gone) this valve assembly may also be a check valve. It may not release air against atmospheric pressure. It may need a vacuum or a specific pressure differential at the threaded port to encourage any air flow. Also part of it may be missing, that nut may have been a lock nut for an adjustment of a piece that is now gone.

At this point you just want the best venting with the parts available today to run the system at best efficiency obtainable. Since you are burning fuel to push the air out of the system to get the steam to the radiators.

Agreed, however in this case it appears the main splits into two branches that wrap around the basement and the far end of at least one of the branches where the last radiator is on that branch is connected is very close to the boiler. The OP could verify this. My illustration does not show this characteristic well.

The illustration was mostly to show the 3 Drips, Wet Return and the Hartford loop connecting into the Equalizer and the boiler's water line.

Maybe the other branch has another main vent hidden where the steam main extension starts.

I think — I hope — that fixing that may be kind of next on the list. Depending on how things unscrew, there are several different ways it could be managed without much difficulty.