The water heater is an 80 gallon Rheem Hybrid Heat Pump device. The waste line that is directly above the water heater is a 3” Schedule 40 pipe that feeds into a 4” Schedule pipe that goes to the septic system.

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    Condensate is supposed to drain above a p-trap's water line.
    – MonkeyZeus
    Jun 9 at 19:09
  • Ken - are you talking about adding a wye (3x2 or 3x1.5) and a trap, or something else? Something else is (broadly) not OK. A wye and a trap are fine, generally, assuming the venting requirements are met.
    – Ecnerwal
    Jun 9 at 20:01

The place where the pump enters the waste line would need to have a trap and a vent just like any other fixture. Seems like a lot of effort for a condensation line.

An easier, maybe ugly way to do this would be to pump into the open side of an existing fixture (toilet or sink) in the level above.

An even easier approach would be to pump to the outside. Obviously if there is an existing nearby sump pit you could just drain into it but then you probably wouldn't be asking this question.

No matter how you go, you need a failsafe way to make sure that if the pump fails the water will not back up into the water heater. The condensate line should have an open end that drains into an open container. The pump should pump from there. The container should dump on the floor before the water level reaches the end of the condensate line.

Depending on the environment, the condensate may evaporate before it collects enough to be pumped so the whole mechanism may behave more like a basement humidifier, which is almost certainly something you don't want.

  • MonkeyZeus, Ecnerwal and Jay613 - thanks very much for your responses. If I simply install a vertical pipe with a wye for a condensate line (pumped up from the floor with a condensate pump), with the wye being 6 inches below the top of the pipe, then a trap and wye connected to the waste line 45 degrees off of the top of the line , would that work? The water heater will only be producing around 32 ounces (max) a day in the summer.
    – Ken M
    Jun 9 at 22:01
  • @KenM I don't fully understand your proposal. You should consider adding a picture to your question which shows your current plumbing setup.
    – MonkeyZeus
    Jun 10 at 13:20
  • You need to think about siphoning and venting two ways. 1: The traditional one, as your new pipe enters your main line, the water flowing out of the trap could siphon the trap so you need venting as with any entry point. 2: Reverse siphoning from your pump line. You'll have what, 7 feet of head coming back from the trap to the pump. When the pump stops it will want to flow back and THAT will siphon the trap. You could put an anti-backflow valve right after the pump or you could put another air gap at the top of the riser line but like I said, this gets awfully complicated for the purpose
    – jay613
    Jun 10 at 15:17
  • You may be able to design this with the trap at the basement floor, basically copying the design of a macerating upflush toilet. In that, the pump is inside a sealed chamber with an up-spout that goes to a Y into the main line with no trap or vent. The toilet bowl acts as the trap. I wonder if you could follow the same design principles?
    – jay613
    Jun 10 at 15:23

Copy an existing design

Here's another answer with an approach to doing this the way you want. I'm not advocating this, but I think it solves some of the problems.

The design is stolen from a macerating toilet. In the photo you could analogize the small vessel collecting condensate via an air gap to the toilet bowl, and the trap to the toilet's serpentine trap. The rest is identical, except maybe your chamber and pump are smaller.

I'll just say again: this seems more complex than is warranted. I'm just thinking through solving the problems if you insist on doing it. Isn't there an outside wall somewhere?

enter image description here

  • Incorrect as drawn, the AAV should be higher than the top of the collection bowl.
    – jay613
    Jun 11 at 13:48

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