Dripping lots of water from the main line air vent

matt_noonan · March 29

I have a one-pipe steam system in my house that has been giving us a lot of trouble this season, with banging and squirting vents. I replaced the squirting radiator vent, but the main vent has also been dripping a lot of water. I have probably emptied the steel bucket below this vent 10 times, though the counter shows that there is not any make-up water being added to the system. I'm hoping to better understand what is going on. Also, is the vent in the correct place? In We've Got Steam Heat and other places I see diagrams that show the main vent inline before the drop back to the boiler, but this one is on a tee just past the drop. Is that ok?

Jamie Hall · March 29

Well… the vent location is marginal. Is that the end of the steam main coming back around to the boiler? It is possible that water flowing in that line sometimes goes up against the elbow and is forced up into the vent.

That said, the vent should not be dripping like that. It's probably done for.

What cutout pressure is the boiler set for? shouldn't be more than 1.5 to 1.7 psig…

matt_noonan · March 29

Right, that's the end of the main there, just before the boiler. The cutout is set to 1.5, though the pressure gauge is showing more like 3 to 4. I'm assuming that gauge is out of whack somehow, because as far as I can tell the boiler should never run if the pressure is really at 3 psig and up.

Jamie Hall · March 29

The pressuretrol may not be responding. How long has it been since you made sure the pigtail was clean and clear all the way into the boiler?

Which is not to say that the pressure gauge is accurate, either… particularly if it's the 0 to 30 psig variety.

JUGHNE · March 29

Your pigtail under the pressure control may be plugged. This would not allow the control to feel the actual pressure. Have you cleaned it lately.

If the gauge goes to zero when cold it is probably working as well as it can.

You should consider adding a 0-5 PSI gauge on the pigtail.

clammy · March 29

Have you checked to make sure your piping to the pressuretrol is not clogged ? Possibly install a 0-3 psi gauge aside from the required 0-30 gauge . Clean sight glass assemble to ensure that the boilers water level is accurate . Try to flush the return drop it may be full of mud . It looks like all your piping is copper hum . I agree that the vent is not in the correct location and it looks like you may have another dry return if i see correctly . It also looks as if the installer did not pipe the return into a hartford loop but looped and can right into the boilers return but the picture could be deceiving . Weil gives a pretty clear diagram of how the near boiler piping should be done in the installation and operation manual which if it was not left w the boiler can be obtained online and compared to what was done . Also i believe weil states to pipe boiler in steel pipe not copper . I would image your basement must be quite warm in the winter and un even heat the standard for steam and fairly high gas bills? Check the i n o manual and pick up one of dans books for starters . That is if your gonna stick w steam .

peace and good luck clammy

109A_5 · March 29

To me that is a lot of water from multiple places, are you sure the boiler is not flooded ? Feeders often don't measure actual water volume they measure time that the feeder's valve is energized and the water flow is through a calibrated orifice to yield 1 gallon per minute. So if the feeder or bypass valve has a slow leak the water keeps coming without registering anything. Also 3 to 4 PSIG may be an indication that there is 7 feet or more of water in the system (leaking vents). Does the sight glass show the proper water level ???

What happens if you shut the boiler off, let it cool and drain it down completely then refill it to the proper level in the sight glass then turn it back on ? Then monitor the water level closely.

Pictures of the sight glass ?

matt_noonan · March 30

The sight glass was pretty opaque, so cleaned it and reinstalled it, and it filled past the top. So I ended up draining the whole system, took apart the pigtail and cleaned it (it had a bit of gunk but not too bad), and refilled to halfway up the sight glass. The gauge never went below about 2.8 psig even when it was sitting on my workbench, so I think its calibration is messed up. I'll get a replacement later this week.

The boiler is running through its first cycle now and everything looks pretty good. The water is bouncing about an inch in the sight glass, but there is much less clanking, no radiators spitting yet, and nothing from the main vent either. I suspect you are right that there was way way too much water in the system.

clammy I think you might be right about the return being clogged too. It has a valve on the bottom of the return but I can only get a few drips of dirty water to come out, even though the valve is well below the water line and should always have water as far as I can tell. Is that a job for the pros?

109A_5 · March 30

You may be able to get a garden hose (with a washing machine (F-F) hose as an adapter, or the like) on the drain spigot and back flush it a bit to work the crud and muck loose. Seems that system is excessively contaminated. The cleaner the water and the pipes the better it will work. That main vent may need cleaning or replacement too. Valves contaminated with rust, etc. don't work well.

Gauges fail all the time just replace it, the 0-30 is for safety. If you are curious, you could add a second low pressure gauge 0-3 or 0-5 with a shut off valve to better see the actual working pressure.

matt_noonan · March 31

So if the feeder or bypass valve has a slow leak the water keeps coming without registering anything

I think this is the root cause! I carefully watched the water level yesterday and it went up by 1cm over the course of a few hours. I shut the valve leading to the feeder and bypass, and watched it again: no change in water level. So it looks like one of those two has a slow leak which was leading to the boiler flooding and water getting backed up way into the main return. Thanks for the help figuring this out!

Dripping lots of water from the main line air vent

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