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When I bought my home, the basement dehumdifier hose was just draining into an open wye off a drain pipe in the floor which also goes up to the kitchen sink drain. Since then, when I had air conditioning installed, the installer also put the drain hose for the condensate pump into this same pipe. (They probably should not have done this, but I guess I can't blame them since there was already something draining there).

Since the basement is mostly finished and livable space, I'd really rather not have an open pipe just sitting there. Both for the potential of entering sewer gases and possible backflow.

My currently plan is to connect the wye to a reducing bushing and then add a check valve to prevent backflow followed by a condensate trap. The dehumidifier would then drain into the condensate pump and the condensate pump drain line would just rest inside the vertical part of the open P-trap.

I'd like some feedback on this approach and whether it will be successful at preventing backflow and sewer gases from entering my home. My main concern is whether there will be enough pressure to actually open the check valve and have it drain properly. My alternate plan is to forego the check valve and simply add a good length of vertical pipe before connecting the condensate trap so there's room to absorb some amount of backflow before spilling on the floor.

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  • That wye was originally intended as a cleanout, I'm guessing
    – user28910
    Nov 4, 2022 at 18:13
  • is your p-trap also your condensate trap? I did something similar for a hrv condensate drain... Y to backflow to p-trap to hub, my hrv condensate was in 1.5" abs so I put a dishwasher drain piece and the surgical tubing from a dehumidifier to the dishwasher port and then had a 90 dump air gapped into the hub. Nov 4, 2022 at 21:52
  • @user28910 I'm sure you're right about the cleanout. Very odd that it was never capped though. Nov 5, 2022 at 0:19
  • @FreshCodemonger There's no trap at all currently, but that was my plan. Nov 5, 2022 at 0:20

1 Answer 1

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Your project:

My currently plan is to connect the wye to a reducing bushing and then add a check valve to prevent backflow followed by a condensate trap. The dehumidifier would then drain into the condensate pump and the condensate pump drain line would just rest inside the vertical part of the open P-trap.

Looks fine BUT

do not forget the original purpose of the Y

Once upon a time the drain might get clogged and the access port for the snake is in the Y.

What ever you do, do not use glue, but a tread system, so you can access the snake port easily if needed.

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    Good reminder that it's probably intended as a cleanout and that I should make it easily accessible. Any thoughts about whether a check valve would actually work without a closed system. It says it's rated to open at 1 PSI, so I'm hoping that would be enough. Nov 5, 2022 at 0:22

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