Need to Drain Water from Steam Heat Radiators

January 29, 2015 1:29 PM

Our heading system got flooded and now there's tons of water in a couple steam heat radiators that are in the wall (not sticking out like so many). Every time it starts heating the water bangs up against the metal and makes huge, scary banging noises. With a normal radiator I would shim up a side so the water runs out, but these are embedded in the wall. I need help identifying which part of the radiator to unscrew to drain it.

OK, there is the intake pipe (picture) heading in to the radiator from the boiler (or last radiator), and it has a knob you can turn to stop steam from getting in the radiator. I'm pretty sure that is NOT where to drain the line.

On the other side there's the pipe heading down back to the next radiator (pic) that has a large nut on it. I suspect that's what I want to open, but just want to be sure.

Any plumbers out there want to give a little free advice?

posted by nathanrudy to Home & Garden (5 answers total)

Any water in the radiator should drain without you having to do anything. The steam is constantly condensing in the radiator (that is primarily how it transfers its heat) and then the condensate returns to the boiler. If the radiator is shifted due to the flooding so that it no longer drains then one end will need to be shimmed to get it back to a draining orientation. What is more likely your problem is a clogged air valve. When the steam rises the air valve opens to let the steam push the air out and fill the radiator. A new air vent may be in order which might be difficult if it is buried in the wall.
posted by caddis at 1:44 PM on January 29, 2015 [1 favorite]

Is there a little square or other geometric-shaped-valve at the top corner of the radiator itself? If so, you can use it to release air trapped in the system. How to bleed a radiator
posted by Pallas Athena at 2:35 PM on January 29, 2015

that's a two-pipe steam system, shimming is only for one pipe steam system. for your radiator the steam enters through the pipe with the control knob on it and the condensate leaves through the other pipe, which will be sloped downward somewhere...

it doesn't have a pressure release valve per se but a "steam trap." if you are having problems with your boiler you will probably have to turn it off and drain the system there. if the radiators ae going cold, it's possible the trap has failed...
posted by ennui.bz at 2:49 PM on January 29, 2015 [1 favorite]

(the trap is on the condensate return side of the radiator)
posted by ennui.bz at 2:50 PM on January 29, 2015

Response by poster: We actually just had a brand new boiler put in, as other news with the system.
posted by nathanrudy at 4:44 PM on January 29, 2015