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Clogged Return

I have a 2 pipe steam system. I replaced the boiler 7 years ago. This year I noticed that after working fine initally, one evening my system was short cycling and radiators were not heating properly or heating at all. I checked my 4 wet returns and found that 3 of the 4 were hot to touch when system was running. The fourth was cold. When I opened the union water flowed out, steam filled pipe, and system began to run properly. I back flushed the return from the boiler and the water in the sight glass dropped from where I marked it. When I reconnect the union, the system would no longer operate properly. Is my underground return clogged? If so can I flush it? Attached are pics of the problem wet return pipe and the return to the boiler.


  • Rod
    Rod Posts: 2,067
    Check Main Vents First

    Hi- Have you checked the main vent on the "clogged"return ? It seems to me that you might be air locked from a none functioning main vent.

    Underground Wet Returns- Attached is a diagram of a flushing setup for an underground wet return. Buried returns are always a potential problem either due to corrosion or from the fact they are the lowest point in the whole steam system so dirt and crud naturally collect here.

    - Rod
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