2 pipe steam fitting

2pipesteam

Home built in 1900. Two pipe steam with a natural gas boiler. No visible trap on the return side of any radiator. There is one main vent at the boiler on the return line. Each radiator has a Hoffman 1A 1/8” vent opposite the supply/return side of the radiator towards the lower third of the last radiator column. Radiators click and chirp and I’m trying to find the culprit. Radiator is properly leaning toward the return, pipes have space to expand and Contract. I found this fitting underneath the wood floor. Does anyone know what this is? It is on the dry return side of the line of each radiator underneath the floor.

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pecmsg

that’s a check valve

The direction of flow is right to left.

2pipesteam

Thank you!

mattmia2

the better question is why?

Jamie Hall

And the other question is — why are there air vents on the radiators? There shouldn't need to be, if the outlets go into a dry return.

The maximum cutout pressure for that system should probably be no more than 0.5 psig (8 ounces).

EBEBRATT-Ed

Someone probably added the rad air vents. Shouldn't need them but I guess they can do no harm.

Check valve are probably to prevent any steam in the returns from backing into another radiator but it the pressure is where it should be they shouldn't be needed.