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a-c drain line misbehavior

I am a homeowner who is not technically inclined or handy. I'm here in a heat wave and my air conditioning is misbehaving and I'm wondering if there is something I can try while I wait for the HVAC appointment. My problem: The A/C is working but the condensate pump is cycling endlessly in an alarming manner.

I have a Beckett CU automatic condensate removal pump attached to the side of my a-c unit. (It is a-c only, no heat.) I opened it up according to the owner's manual and cleaned it out. I checked the floats and valves. It was a little dirty, but not too bad. The motor looks pristine. This did not affect the problem. I blew into the line (yuck! do HVAC guys do that?) and found it was plugged and not moving air.

I traced the condensate drain line (a 3/4" plastic tube) outside and found that the drain end was buried in the ground. I cleaned it out and blew into it (also yuck!) to see if it was clear. I can now move air through it but it is hard work! It doesn't seem ideal.

At first I couldn't figure out why the drain pan wasn't just filling completely with water and shutting off the unit with the safety float. Here is my thinking: The pump seems to be able to move the water up the line into the attic. But then it pours back down, filling the pan, starting the pump, and sending it right back up again. Since the drain line is in fact now dripping water to the outside when the unit is operating, some of the water seems to make it, and that's why the pan doesn't overfill with water and shut off the unit. But most of the water comes back, so the pump is cycling constantly (~every 60 seconds).

It strikes me as an incredibly long run for a drain line (but what do I know?). It goes up into the attic ceiling, across the entire diagonal attic distance of my large old house, then down three stories. I would guess there is no inverted "U" shape above the pump as there is supposed to be to create a hump the pump can push the water past. Probably the run across the attic is therefore too flat and the lack of elevation is the problem, causing most of the water to come back to the pump.

I'm sort of proud of my detective work, but I don't know what to do now. The area just above the a-c unit where the tube leads is inaccessible. If I try to get at it from the crawlspace, the area just above the a-c unit (where I think the inverted "U" should go) is blocked by a metal a-c duct that takes almost all of the height of the crawlspace. I don't know how to get behind it.

Is there some insider knowledgeable HVAC professional tip that can help me in this situation? If I shut off the a/c it almost immediately becomes 103 degrees in the top part of my house. If I leave it on the pump cycles endlessly and I fear for it. Any ideas?

Hopefully yours,



  • Techman
    Techman Member Posts: 2,144
    condensate pump

    There should bean inverted trap  in the drain coming out of the air handler. The cond pump should have a check valve in it to prevent back draining and short cycling of the pump.All cond pumps have a certain height of "lift " so detective out which pump you have and its lift. The internal check valve can get stuck/lodged open/leaking.At worst,replace the pump and keep the old one for a spare .
  • niftyc_2
    niftyc_2 Member Posts: 34
    no replacement check valves to be found

    Techman, I don't understand how inverted traps relate (or what they are), but I do understand the check valve comment. Thanks so much! I identified the check valve in the pump and looked at it indeed it does not check anything -- it is moving water freely in either direction.

    It looks like my pump (either a CU-14 or CU-19) is too old to obtain this replacement part. The Beckett web site makes it look like the part is no longer made. Looks like I need to replace the pump.

    REALLY appreciate your help,

  • Ironman
    Ironman Member Posts: 7,076
    Pumping 3 Stories?

    Am I mis-reading or are you saying that the pump is in the crawl space and it's pumping water up to the attic and then draining it back down 3 stories?

    I don't know why anyone would do that and most condensate pumps don't have that much lift. Why not send it directly outside from the crawl space?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • niftyc
    niftyc Member Posts: 17
    It seems weird to me too!

    Hey thanks for posting Ironman! It seems weird to me too. The indoor unit is actually in a third floor semi-finished attic room.

    The condensate drain line probably goes on this long route because it is strapped to the pipe that goes to the external a/c unit (don't know what that is called). This external unit seems to have been located as far as possible from the indoor a/c unit. I have no idea why this is set up that way.

    So yes, the condensate drain line travels from the pump on the floor of the 3rd floor attic, straight up through the ceiling and into a crawlspace (a one story rise), across the entire house diagonally (running mostly horizontally), then down three stories on the other side of the house.

    I take it this is not the best way to do it?

  • Ironman
    Ironman Member Posts: 7,076

    The only or simplest way the installer saw to do it. Remember, we're not seeing how your house is laid out.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
This discussion has been closed.