End of the Line

Kenaroni

I'm happy to have found your site and have learned a lot by watching your videos and reading this forum. I have a particular question that is defying my ability to solve. I live in an 8 unit townhome apartment building. We have a one pipe steam system that has given me little problem over the past 20 years.

My unit is at the end of the line, at the opposite end from the boiler. We've checked for pipe sags, and the slopes appear good. Last winter I started to experience water build up in my pipes and radiators that would result in banging, spitting vents, and lack of any heat. Since then our service technicians have cleaned the steam traps, and installed new Hoffman 74 vents in the middle and end of the main steam line. I have replaced or cleaned my radiator vents.

What I am experiencing now is that after somewhere between a few hours to three weeks or so of problem free operation, I'll start hearing water gurgling in my front room radiator. If left alone, this will increase and it appears that the radiator then fills with water and heat stops. Then the process repeats in my other radiators, with increasing banging.

I'm the only person on this line who is experiencing this problem. When I check the main line vent and the condensate return pipe after the drop, both seem good and hot. When I check the boiler it seems to be operating fine with the same 5psi of steam pressure being created that has been the norm here for years. The temporary solution I have stumbled on consists of shutting down the boiler for an hour or so, to let the pressure out of the line and allow the water to drain back to the boiler. Then after starting back up, I'll get heat for some indeterminate time until the water accumulates again.

Can anyone point me to a possible solution? Based on watching the videos here, I suspect that the steam pressure may be set too high. Otherwise, I'm at a loss. I'll appreciate any tips you might provide. Thanks!

neilc

for starters,
5 psi is too high,
dial it down to <2.

do you have that boiler access and control ?
post some pictures, floor to ceiling, from a couple different angles, of the boiler,
when was boiler, Ptrol, and pigtail serviced last?
who is checking the water levels?

Jamie Hall

Well, the pressure is too high -- 2 psi would probably be ample, and slghtly less might work as well.

However, that may not be the problem. You mention steam traps. These are not really all that common on one pipe steam systems -- they aren't usually needed. Where are they, and how are they piped? You mentioned that they were cleaned -- but have they been checked to see that they are actually operating as intended? That is -- letting condensate (and sometimes air) through, but not steam? One reason for my asking is that you also mention that the "condensate return pipe" is good and hot. It shouldn't be. Warm, yes, perhaps warm enough even to be hard to hold for any length of time -- but not hot.

Also in relation to the condensate return pipe, it seems to me possible that your condensate is slow to return -- possibly really slow to return. Is it possible to get at the return pipe and flush it out?

Ironman

If a radiator is filling with water on a one pipe system, the radiator or piping is not sloped properly. This, plus the pressure being too high can cause water to be in places it shouldn't.

I'm a little puzzled with your statement about traps on a one pipe system. Where are they located and what type?

Pics would be very helpful.

EBEBRATT-Ed

@Kenaroni

Obviously something has changed. I agree with lowering the pressure but that is unlikely to be the fix if it's always been 5 psi.

I would take the pressure control off and have the pigtail and connection to the boiler cleaned out.

You mentioned steam traps. Do you have a condensate pump? I know you said the traps have been serviced check and see if you find a trap that is cold or cooler than the others.

Someone may have replaced a trap and made a substitution.

Maybe a pipe hanger fell off and a pipe is sagging

Maybe someone is hanging laundry on a pipe

A 3/4" trap from 1 manufacturer will not have the same capacity as a different trap. Trap orifice size determines capacity , not pipe size

We all know the problem you have a radiator and a run out that is holding water.

The question is why

Pitch of radiator
Pitch of piping
Bad trap
Bad air vent
Plugged pigtail allowing higher than normal pressure
Higher water line in the boiler


Also, if you have a condensate tank when the boiler is up to pressure and see if steam is coming out of the vent or overflow. This could point to a bad trap blowing steam which would pressurize the returns and may cause your radiator not to drain

If there is no condensate pump check that the return lines are vented and that the vents work

Kenaroni

Thanks for all your input.

When the technicians were out to service our system in the fall they referred to several devices near the middle and the end of the line as "traps". They also called them filters. They appeared to me be basically a covered pot containing a wire mesh screen liner, with connections near the top for condensate to enter and leave. Our building is about a hundred years old and these have the look of being original equipment. Basically, they were out of sight, out of mind. These had been ignored for years and needed to be cleaned out. I watched for part of the time the technicians were doing this, and it appeared to me that the pot was filled with sludge. In my unit, this device is simply inserted as part of the condensate return line. Around the middle of our building in another basement, the device is piped between both the main steam line and the condensate return pipe. It looked to me that its job was to capture water or sludge moving up the steam line. We've inspected the whole run of the line, and these two are the only ones present.

Having looked at various videos here about traps, it may be possible these things are not really traps at all, but are simply some sort of filter to capture sludge from the system instead?

My radiators are pitched OK. We checked pitch on the pipes in the building last summer and it looked OK. The water level on the boiler is proper. No steam is coming from the condensate tank.

It looks like we still have the plugged pigtail, too-high pressure, and bad vents as likely culprits.

Thanks again to all. If these comments jar any thoughts, please share. This has been very helpful!

neilc

post a picture of this screened device you speak of,

there's a story here about keeping your hands in your pockets, and slowly backing away, when you're not sure of what you're looking at

Rich_L

It sounds like the devices you were originally describing are actually in-line "strainers". These are basically a filter for your piping system.

One question I've not seen asked yet, are your radiator valves fully open? On a one pipe steam system they need to be fully open or completely closed. They can't be used to regulate heat from a radiator. Bearing in mind that a one pipe system uses the same pipe for incoming steam AND leaving condensate, if the valve's partway closed, the restricted space increases the incoming steam velocity and won't let the rad drain correctly. If needed, you can regulate heat output with different size/ capacity steam vents.

Steamhead

@Kenaroni , those Hoffman #74 vents are undoubtedly too small. With their needle-sized orifices, they are designed for venting high-pressure unit heaters, not steam mains. If this type of vent has been in use for years, someone may have jacked up the pressure to compensate. Generating higher-pressure steam takes more water and results in more condensate when it condenses.

Low pressure and large main vents are the way to go. How long are your steam mains and what pipe size are they? Where are you located?

Jamie Hall

I'm a little concerned -- you mentioned that one of these strainer affairs or whatever is connected between a steam main and a condensate return line? Ah... no... I hope not. If it is, what, if anything, is there to prevent steam from zipping over to the return?

Kenaroni

Thank you everyone.

I'll raise the issue of too-high steam pressure and too-small air vents with our service people when they get here. I'll also mention the clogged pigtail possibility.

I do keep the radiator valves completely open or closed at all times. I learned the hard way years ago not to open them partially.

The steam line is covered by insulation, but it looks like it is probably around three or three and a half inches under that. The condensate line is 2 and a quarter inches.

I have attached a picture of the possible filter on the condensate return line. This was opened and cleaned last fall.


Thanks again for all of your helpful insights.

Steamhead

That looks like an Illinois float-and-thermostatic trap, not a strainer. The hexagonal cap on the top is the air venting unit- if you look up there it should say Illinois on it.

Kenaroni

You nailed it Steamhead. It's says Illinois Model 7, Series G. Based on what everyone has said here, should this trap even be on the condensate return for a one pipe system? It looks original, and was there twenty years ago when I moved here. Like I said in an earlier post, it was out of sight/out of mind, and was never serviced for at least twenty years until last fall. The system has worked fine all that time until my current problem arose last year. I'll be calling out service guys out today now that the long weekend is over. I suspect the first step will be installing a higher capacity air vent at the end of the main line, and dialing down the pressure a bit.

By the way, after four days of dealing with a cycle of water filled radiators that were forcing boiler shut-downs to drain ever 4-8 hours, the system has been working flawlessly since 5 last evening.