F&T Traps on One Pipe

Perry Fertig

I own a fantastic old building (not quite a house, more like a church/school combo) with a one pipe steam system. I just had the boiler replaced with a Weil-McLain LGB 11. The old system had a power burner (gas) and a condensate return pump. Unfortunately the pump froze and broke during the time without heat. My plumber (of the type that Dan would call a knucklehead) removed all the pump piping/controls and tried to make the system into a gravity return. He thinks (and I suspect he's right) that this is how it used to be, as the building is old enough to have a full fledged coal room. He left the F&T traps in the lines, but there is no vent downstream of the traps. Now, half the building is cold, and the vents upstream of the traps do not seem to vent (they are brand new.) Is my problem the lack of vents on the outlet side of the traps? Do I even need F&T traps? My plumber thinks I need to reinstall a pump, but I am not sure this is the actual problem and it is another two grand I don't have. Another problem is the fact that he undersized the near boiler piping, but I don't think this is the main problem, as half the building is screaming hot (the vertical distance between the vents and traps on this side is much greater.) Sorry for the long posting, but any and all opinions would be helpful!! Thanks!!

Al Letellier

steam system traps

Awfully hard to answer your question without seeing what's there, Perry. Generally speaking, there are no traps on a single pipe, and you had one because the condensate pump was there. And it was there for a reason, so...??? The cndensate pump is vented to atmosphere and that eliminates any pressure downstream of the trap to allow condensate to flow back to the pump. With the pump out and the trap still in, the pressure in the return lines is giving you the problems. Use the Find a Pro feature here and have one come in to review your system and make suggestions for repair. Your "knucklehead" guy doesn't seem to get it!!

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Perry Fertig

steam system traps and pumps

Thanks, Al. You mostly confirmed what I suspected from what I've been reading. I don't know the answer to why the pump was installed, but you're right, it may have been installed for a reason. But the speed of condensate return doesn't seem to be an issue. The old boiler was a power burner and the new one is an atmospheric burner. Could this make a difference?

Perry Fertig

Portland

Hey Al-
I just looked up your info. My parents are in Portland and I grew up in Yarmouth. I am now in Reading, Pennsylvania, or else I'd have you come take a look at this mess!
Thanks!

Joe_20

Single pipe steam....yes, I've had experience with single pipe steam used for heating tanks. The F&T traps require a lot of maintenance and are often negelected. Our condensate pump, as was mentioned was vented...when the traps were working properly the vent would "puff" a little steam now and then...when the traps stuck open, the steam would pour out of the vent....Recently we put a new boiler in and unfortunately had a bad check valve which let steam/water back into the condensate pump...the water would eventually back up and spill out the vent!!! We ended up sending lots of water to the sewer and boiler chemicals. Steam, little problems cause big issues!!

Fred Harwood

One-pipe

With a clean wet return, plenty of A space, less than one psi steam, and plenty of mains venting, a well-designed one-pipe should need no F&Ts or pumps.