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Do we need Main Vents with Condensate Pump?

sreja Member Posts: 175
After reading Dan's great books I'm still confused about whether one needs main vents even if there is a condensate pump..

As i understand it the condensate pump opens the return line to the atmosphere and has it's own small vent on it where air can escape.

Does this mean that we don't need main vents (this is a 70 yr old building and i dont see any main vents though there are F+Ts)?


  • Brad White_202
    Brad White_202 Member Posts: 105
    It depends

    There are lots of two-pipe systems with condensate pumps and no vents.

    What is distinct about these is that the returns are dry the entire way including into the receiver, at which point the receiver vent becomes the main vent.

    In any two-pipe system with wet returns, each return (in a riser system) would be vented independently and if one large return, that would be a single large vent arrangement.

    Any time a pocket of condensate is possible, it must be vented upstream.

    In SOME systems where this occurs, there may not be a bona-fide air vent upstream of the pocket, but a vent loop which goes over the pocket and connects to the other side.

    An example of this is an otherwise dry return which must drop below a door opening. The air vent loop would go over the door and connect on the other side, providing continuity of venting to the main or receiver vent but not have a vent itself.
  • My question would be

    do you really need the condensate pump? Most of those I see in the field are completely unnecessary.

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  • And.....

    the venting capacity of F&T traps appears to be quite low. I recently repiped a system with new Hoffman F & T traps on both the short and long mains and a relocated condensate pump. I put a small Gorton #1 vent on the long main and it now heats up much more quickly than the short main. Adding good size main vents to a system with F & T traps is probably a really good idea.


    PS. Steamhead, I haven't seen any test data on F & T venting, anybody test them yet?

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  • Check with Gerry

    if I know him, he's already working on it......

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