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Flooding problem! - Two pipe air vent system

Beautiful old building in Marblehead MA with 2-pipe air vent steam system.Complaint by customer flooding system water coming out of 2nd floor radiator vents and packing nuts.
System has worked without problems until past 2 years when flooding has gotten worse.
I was there last week to checks things out. They had drained system back to normal level and with several eyewitness accounts (no two stories were the same)I had to try and do some investigating with little to go by. It seemed like the pump controller could be the culprit.(Recently had the float assembly replaced) the system had flooded after that repair. I dropped the level of the boiler through a drain and watched the function of the pump controller and it seemed to be working bringing the pump and off and the level of the boiler gong up and down as it should. I had no solution at this time. I told the customer to keep an eye on it when and let me know.
I've have sketched out and attached a simplified drawing of piping and components.
Last call from customer described the following scenario:
No call for heat. Possibly ran 4 or 5 days before.(No one is sure)
Water 2nd floor spitting water out vents
Water 2nd floor dripping from packing nuts on steam hand valves
Boiler level above sight glass
Receiver tank level above sight glass
Receiver pump running
Condensate pump on running.
No water coming out of either condensate or receiver vent pipes.
Customer shut off condensate pump switch:
Water pouring out of condensate vent pipe
Receiver pump stops pumping.

Looking for help.


  • Steamhead
    Steamhead Member Posts: 15,991
    Why do you need a boiler-feed pump in the first place? Assuming everything is well above the "A" dimension as the diagram seems to show, that system should work fine using gravity return.

    Post a pic of the false water line and associated piping. That may be holding water up in the system.

    What pressure are you running?

    Are there any TRVs on the radiators?

    Where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • StephenQuattrucci
    StephenQuattrucci Member Posts: 11
    Were you able to open the drawing I posted?

    Im new to the site and trying to figure things out.
  • StephenQuattrucci
    StephenQuattrucci Member Posts: 11
    Pressure is somewhere around 2psi. NOTRV's on the radiators. I'm located South of Boston.
  • Jamie Hall
    Jamie Hall Member Posts: 21,111
    Oy. Well, I'm sorry your south of Boston, because I do know a couple of really good steam people north and west, but they won't work south because of the traffic.

    Now. That said.

    As @Steamhead said, why do you need the condensate pump and associated tank? Why do you need the receiver and it's associated tank? Why do you need the F&T and the false water line? If your diagram is even remotely to scale, you don't need any of them. I'd lose them. Nothing but trouble.

    Assuming that the drawing is correct -- and I expect it is -- then the system has been modified at some point from the usual two pipe air vent system As it is drawn, it is actually a standard two pipe system, since steam will never get into the returns backwards -- they all appear to be dripped to a wet return. Nothing wrong with that -- except that you will have to keep the radiator vents. It probably wouldn't hurt your distribution any to put a good big main vent on the end of the steam main while you are at it.

    Also -- do check the pressure. That system should run just fine on 1.5 psi or less.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • gerry gill
    gerry gill Member Posts: 3,058
    I'm with Steamhead and Jamie on this.. From your drawing there is a boatload of stuff that doesn't need to be there.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

    JUGHNE Member Posts: 10,571
    Does the feeder pump have the city water connection?
    Or is there a manual by-pass fill valve also?

    Feeder pump float valve could be overpowered by the city pressure....often a PRV valve on that supply.
    Manual by-pass, if installed, could be leaking thru.

    Can't understand why the pumps.....unless the return is too slow and boiler runs out of water and the reserve of the feeder pump was thought to be needed......maybe just plugged slow wet returns.
    We assume that both pumps are in the same room at the same level or not?
    EBEBRATT-Ed Member Posts: 13,442
    If the water level in the boiler is high and the feed pumps are running you have a pump control issue. Wiring, float or the connected piping.

    That being said I have seen 2 150 pump controls that would stick and flood the boiler. This was after being taken apart twice, cleaned, flushed piping and pump housing and checking floats and all wwiring. replaced the control and all was well.

    Looks like they probably have had this problem before. Is that an overflow trap piped in the picture?
    JUGHNE Member Posts: 10,571
    I was partly wrong with my first posting.
    If it is plumbed as your drawing then the only source of water into the boiler is the feed pump controlled by the feeder switch, as Ed said.

    However, there could be a manual boiler fill valve plumbed into the boiler itself. It could be passing some water.

    Also, I know of 2 boilers that have the feeder pump control as this....but also have a auto fill LWCO as the redundant safety.
    Those can slyly pass water also......in my case that is where the manual fill valve is also.
  • I apologize for misinformation. I am a contractor South of Boston the job is North of Boston. Thank you for feedback. There is only one source of fresh water and that is a float activated feed valve in the 30 gallon receiver tank. First instincts are that the feeder is leaking by but that would show up as water coming out the vent pipe It has not in any scenario they described to me. It seems to me as well that there have been unnecessary components added to the system. All that being said it has worked in the past and has gotten worse over the last few years.
    If I rip out the pumps and go back to gravity return with a slightly lower boiler water level(Approx 8") what problems could possible have?
  • Jamie Hall
    Jamie Hall Member Posts: 21,111
    The only problem I can see at first glance for going back to gravity at a lower boiler water level is the possibility of drying out a wet return somewhere and exposing the bottoms of some drips. Check that out thoroughly.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • gennady
    gennady Member Posts: 839
    Do you have DHW coil on that boiler?
  • gerry gill
    gerry gill Member Posts: 3,058
    Wouldn’t the cheapest solution be what Ebebratt Ed implied and just replace the offending pump controller?
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.