2-pipe steam

GMash

I have a 2-pipe steam system and a cold radiator on the second floor. The supply pipe is hot up to the valve. Here’s what we’ve done so far; replaced steam vent with new, disconnected the steam valve and checked the seat to be sure valve was fully open (no knobs on stem). Ran the boiler with steam valve off and after a few minutes, steam began flowing out of the supply pipe. A minute later, water began bubbling out of supply. We assume the water in the line is preventing the steam from getting into the rad. Does this point to a clog in the supply?  If not, any ideas?

JUGHNE

2 pipe radiators usually do not have air vents on them....is the vent you refer to on it or is it on the main?

Usually the only clog in a steam supply line is a dip with a pool of water sitting in it.

EBEBRATT-Ed

Sounds like your supply pipe is not pitched correctly. It should be pitched up away from the main in the direction of flow.

Do your radiators have steam traps?

GMash

No steam traps but they all have the auto bleeder vents on them.  This is a 3-story building and all work well but 2.  I just don’t understand how the supply line can be full of water.

neilc

picture of the rad from both ends,
picture of the boiler from floor to ceiling,

Jamie Hall

Two things. First, steam mains do not clog, nor do dry returns (above the boiler water line). Wet returns can, and sometimes do, clog, which will be shown be slow return to level in the sight glass after the boiler runs.

Two, water can't stand in any pipe -- supply line (steam main) or otherwise if it can drain. If water is in a supply line, find out where the gradient is wrong, preventing it from draining.

GMash

IMG_3783.HEIC IMG_3784.HEIC First pic is Right side and second pic is Left side of radiator. When boiler runs, the pipe UP TO the valve is hot but it’s not getting through the valve. We disconnect the valve and ran the boiler again. Steam flowed out of the valve for a minute, but then B.c. water started bubbling out of the pipe. Anybody know why??

Jamie Hall

Somewhere just below the valve there is a horizontal section of pipe which isn't pitched properly and is holding water. It may not be that long a section, and you might be able to raise the radiator enough to give it enough pitch.

GMash

This is a second floor radiator. The pipes go down through the floor and down the wall to the basement. In the basement, there is an offset. Working backwards from the main return, I can see the pipes for the first two feet are straight up, then they angle over through a crawl space and up. There are other radiators that are set up the same and they work fine. Where else could that water be coming from and is that water in fact blocking the steam from entering the radiator?

ethicalpaul

The water comes from the condensation of steam in the radiator and in the pipe itself. It must be able to drain back down to the boiler.

If any "valley" or "dip" in any pipe allows it to collect, it can cause hammering and yes, it can prevent or reduce steam from reaching the radiator.

nicholas bonham-carter

See if you can raise up both ends of the radiator, (which may restore the proper pitch of the supply pipe)-Evan a half inch.
Quarters, or checkers can be used under the feet.—NBC

GMash

We actually noticed that the radiator is pitched to the left (opposite the supply) about an inch, and I assume that is the reason. When we disconnected the radiator, water came out of the left connection, but not a tremendous amount. The surprising thing is, when we forced the boiler to run by jumping the thermostat, the supply pipe got hot right up to the valve, but no further. This led us to believe the valve was not opening, which is why we disconnected it. They both open and close fine.

Jamie Hall

Does sound like the valve isn't opening. Are you sure that the little disc on the valve which seals against the seat but lifts when you open the valve really is lifting? They do fall off sometimes...

GMash

My thoughts exactly, but my mechanic said they were definitely opening. He thinks it has to do with that water that came out of the supply pipe, blocking the steam from getting into the rad. So of course I said, where the hell is the water coming from and why is it not getting down to the main return?

Jamie Hall

How did your mechanic verify that the valve was really intact and opening? Other than taking the bonnet off the valve and looking in there and at the valve itself, I don't know of any way.

GMash

That's what he did, he took it off and turned the stem and we could see it move up and down.

JUGHNE

You may have seen the disc move up and down.
Sometimes the rubber washer, which is cooked by now and hard as a rock, falls off the bottom of that disk and is lying on the inlet port. That would allow some steam in but prevent water from draining back.
To really see this the entire top of the valve and stem needs to be removed. Then you should see the top of the supply pipe opening.
Or disconnect the rad and move it away to look inside the outlet of the valve.