One Radiator not working

Nickocto

Hello,
Hoping for some advice here. I have 1 radiator in a bedroom on a 2nd floor apartment in MA that does not work. There are 6 other radiators in the apartment that work well. Separate boiler for this floor.
After messing with it for quite some time this weekend I was able to get the pipe hot all the way to the radiator, some steam coming out of the valve, and the first section on the radiator warm (not hot enough to heat the room). Last winter this pipe wouldn't get hot all the way to the radiator. It would get very hot from the basement, through the first floor, and lose heat in the floor beneath the radiator. There was quite a bit of gurgling going on in the pipe as well this time.

This is a 2 pipe radiator. Most in the unit are one pipe, however. It has a vent on the side. I was able to take off the valve and confirm no blockage there. Left the radiator and valve off for an hour while running heat. I imagine a properly working radiator would let out lots of steam with nothing there to stop it which it did not. I was also able to snake a cable in past the first 2 elbows into the pipe that runs straight to the basement. It didn't seem wet when I pulled it out indicating water in the pipe.
Few questions that may help me trouble shoot.
1. There is a horizontal pipe that runs under the radiator for the steam supply line. How much should this be pitched?
2. How much should the radiator be pitched itself?
3. I'm worried the 2nd elbow may be clogged. I have access to the pipes if I rip up some of the flooring as pictured. I can take off the valve but I can't take off the next pipe which is a small vertical run, to then try to spin the horizontal pipe and get to the elbow. Any tips on taking off a small straight pipe (pictured) that wont budge? Having trouble gripping it with the pipe wrenches. Or is there a snake/pipe cleaner I can use to try to possibly free some debris?

Any suggestions or thoughts here?

Nickocto

adding pictures here

ethicalpaul

1. It doesn't have to be extreme...like 1/4" per foot or greater? Really on a short length, even level would probably be OK, but some slope is definitely good. What you REALLY don't want is reverse slope. I see you heard gurgling. Odds are, you have effectively a water trap under your radiator which is blocking the steam.
2. Maybe a quarter to 1/2 inch over its length, depending on how long it is. You can't slope it too much else it will put your pipes under a lot of stress, or misalign your valve union.
3. It's almost certainly not clogged. Far, far more likely is that the floor or house has sagged and what used to be a nice slope on that horizontal in the floor joists is now a reverse slope and standing water is killing the steam. There's really no debris that can clog a radiator supply pipe.

Your picture(s) didn't come through, so maybe try to edit your post to include them.

After messing with it for quite some time this weekend I was able to get the pipe hot all the way to the radiator, some steam coming out of the valve, and the first section on the radiator warm (not hot enough to heat the room).

How did you mess with it?

I had a very similar situation, but my "trap" was in my basement (it was possibly in my floor joists too, but I just re-ran the pipe completely. You will see some tips in this thread for things to try. Raising the radiator is a possible fix. (this re-slopes the pipes correctly if it works)

https://forum.heatinghelp.com/discussion/167233/fixing-pitch-issues-in-old-house/

Paul Pollets

You're going to have to insulate the pipes and fittings from the boiler header to the farthest radiator with a min. of 1" fiberglass to have this system work properly. If you don't, it's likely the steam has condensed before it gets to the top of the system. The steam pressure should also be lowered considerably. Read "The Lost Art of Steam Heating"...it will help you understand the system.

ethicalpaul

Respectfully, @Paul Pollets I have uninsulated 1" supply risers running in uninsulated exterior wall cavities that heat their radiators just fine (although I hate the idea of heating that exterior space). It was a reverse slope horizontal section that killed 100% of the steam trying to get to that radiator. (edit: that radiator of mine I mean)

I agree completely that insulating all the steam supply lines would be ideal, but it can't be uncommon for it to be otherwise.

Paul Pollets

The near boiler piping is not insulated. That has to be done on a steam system. Having uninsulated risers in an exterior wall compromises the steam delivery. You can take a walk outside without a jacket or hat when it's 15 degrees out, but it's neither comfortable or efficient...

Jamie Hall

Agree with @ethicalpaul here, @Paul Pollets . I have several buildings with steam heat. The mains are all insulated -- helps a lot -- but the risers to the second floor are not. None of them. Does it slow the steam going to the upstairs radiators? Probably, a little. Does it stop it? No. Hardly.

However, if there is a water trap as he suggested, that will do it every time -- and it doesn't have to be much of a trap. In the present instance, it looks to me as though we have a very old two pipe with air vent radiator -- not a two pipe with return (the tip off is the two low placed identical valves on either end of the radiator). But I also see a very sad looking pipe in the third picture which partly buried in the debris. Any idea what that connects to? On either end?

And what happens if you run the boiler up to steaming with the radiator gone and disconnected like that? (Please have someone in the basement to turn the boiler off right now if steam actually does appear at the disconnected pipe and valves!). If you don't get steam at the disconnected pipe and valve doing that, you're going to have to look elsewhere in the piping for the problem.

ethicalpaul

That would be a good test that Jamie recommends. You'll be able to see and hear what is going on.

I can see by your picture that the horizontal is in a hole drilled through the joist, so you won't be able to change the slope there by lifting the radiator, sorry about that.

Nickocto

Thanks for the advice. I think I am going to notch that floor joist that the pipe runs through to be able to increase the pitch on that horizontal pipe.
Yes, none of the mains are insulated currently. Use to be with asbestos but I had that removed a few years ago. Ill look into that also.
When I "messed around with it": I took it apart a couple times. Let the heat crank for a couple hours. Snaked it with a few different snakes. Tried to increase pitch of pipe. Banged on it hoping to knock off some rust... things of this sort.

EdTheHeaterMan

Why are there 2 supply valves? Did someone try to fix this problem a long time ago by adding a second supply pipe to the other side of the radiator?

How difficult would it be to run a new riser with the proper pitch starting at the main, all the way up to the radiator? Many steam systems have exposed piping from the basement to the radiator. This would eliminate any question of clogged piping. You could make all the proper swing joints for proper pitch and make sure everything is correctly installed to that radiator.

ethicalpaul

It’s a good thing to look into. I reran mine but be careful—now mine’s too hot often 😅

see https://forum.heatinghelp.com/discussion/177777/autumn-saturday-radiator-repipe

Jamie Hall

The two radiator valves, @EdTheHeaterMan , suggest to me that that radiator was piped as a two pipe air vent system -- came before traps were invented. They do work... they really are more one pipe steam systems, but the idea was that the condensate would go out one end (the one with the smaller pipe) and come in the other. It worked. Sort of. There's a section on them in Lost Art.