I have a new bar sink in my basement. The only remaining jobs are to tie the pex lines into the main water lines and to connect the sink drain to the sewage pump. The part that has me a bit troubled is preferring to avoid opening the sewage basin, or drilling a new hole in the top. I noticed the basin has a vent pipe and was wondering if it would be permissible to connect the drain from the sink into the vent pipe using a wye fitting.

UPDATE: I went ahead and did it, and it has been working and properly pumping just fine.

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In the image below the pipe on the far left can be ignored, as it is for the sump pump. The pipe on the far right is the sewage pipe, and the pipe in the middle is the vent pipe.

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If I were to do this, would it be to code? Or would it cause problems when eventually selling the house?

If not, is there a relatively simple alternative that wouldn't require a new hole in the sewage basin lid?

  • 2
    That looks more like a sump pit that is meant to pump away groundwater, nothing to do with sewage or gray water (non-toilet waste water). Commented Feb 27, 2023 at 17:28
  • 1
    You may be right. But interior sewage discharge pumps I've seen have been free standing, for ease of servicing & replacement. Exterior ones (called grinder pumps in some parts of the country) I've come across are in a buried concrete lined pit, sort of like a septic tank.
    – SteveSh
    Commented Feb 27, 2023 at 18:18
  • 1
    Another consideration: If the bar sink is not used frequently, you must ensure its trap remains full or else it will become the vent for this pit.
    – jay613
    Commented Mar 1, 2023 at 20:25
  • 1
    Yes, what you did will probably work OK, irrespective of what the plumbing code says. The one problem I can see is the pump, when it discharges, could suck the water out of the P-trap under your new sink. That is, if it hasn't already been emptied due to the long run and drop of the drain pipe
    – SteveSh
    Commented Mar 6, 2023 at 17:17
  • 1
    @person0 - That's the right thing to do, and should prevent the problem I was talking about. So now you have two vents into your sewage pump? One's the original, and a new one from the vent that was added as part of the sink install?
    – SteveSh
    Commented Mar 6, 2023 at 17:41

1 Answer 1


On second thought, despite my earlier comments, it could be a sewage discharge pump that's installed in the floor.

The one house I had with a sewage pump had the pump free standing in a utility room at the lowest level of the house. Here's a couple of pictures of the installation:

enter image description here

enter image description here

Note that is says both the vent and discharge pipes are 2" diameter. The discharge pipe is the one wrapped with insulation. The sewage intake is the bigger 3" pipe on the lower left of the housing.

This plumbing arrangement is consistent with OP's setup.

  • Yes, the basement plumbing with the 3" pipe feeds in below the concrete. That is my understanding. Thanks!
    – person0
    Commented Feb 28, 2023 at 1:35
  • This doesn’t actually answer the question that was asked.
    – nobody
    Commented Feb 28, 2023 at 2:02
  • I know. But most of the comments had to do with whether this was a sewage pump or not. Until that could be established, the question was not relevant, in the sense that it would not be applicable to a standard sump pump.
    – SteveSh
    Commented Feb 28, 2023 at 2:49
  • This is an unusual use of a sewage pump. The most common is to pump out a basement bathroom, including a toilet that is on the floor and so the pit obviously needs to be under the floor. In the above situation, it appears to receive its contents from the floor above? Is that right? Meaning the ground floor also requires pumping? Or perhaps this pump is in a sub-basement? Or the lower half of a split level and the bathroom is in the upper half and the sewer pipe is even higher than that? At any rate it's not typical.
    – jay613
    Commented Mar 6, 2023 at 15:05
  • 1
    @jay613 - I assume you're referencing my post & pictures? Yes, the pump is receiving effluent from the floor above it. And yes, the sewer pipe is higher than that. The house is down hill from the street, along which the waste water (sewage) pipe runs. So the effluent needs to be discharged higher than the basement floor in order to reach the elevation of the main sewer pipe. This is typical in many locations when the public sewer hi higher than the house's outfall.
    – SteveSh
    Commented Mar 6, 2023 at 15:26

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