Adding Toilet and Sink to Basement

Help Support Plumbing Forums:


New Member
Dec 4, 2021
Reaction score
We live in a pretty basic bungalow home with only one bathroom. I want to install a basement toilet and sink. As there is a utility sink I the basement, the most important part is the toilet. The space s super tight, so any horizontal bends would make it near impossible. I am trying to avoid bends and line up a perfect straight shot.

I made a diagram of plumbing for the house and added a few photos. The only place I think a toilet would physically fit is about 8 feet from the 4" Clean Out cap. This cap is 10" on center off the ground. I have the ability to completely do the plumbing and then recreate the wall as it's just a basement retreat, so not real construction constraints beyond just a small amount of space.
Here are things I wonder about, but I bet there’s more I haven’t even considered so appreciate any advice. Also I have zero ego here, so feel free to let me know I am crazy or likely to destroy our house.

  1. Can I tie the toiler directly into the drain pipe at the clean out cap?
  2. If I can tie in that way, do I need to make another clean out cap? I may not have the space to do this if clean out caps have to be at the very end of a run (please excuse my ignorance)
  3. Based on the plumbing diagram, do I need to vent this toilet, or would the existing vent suffice?
  4. If I do need to vent, can a vent be done near ground level? I do have access to a discrete exterior wall where this could go.
  5. Does the toilet outlet need to be higher or level with the drain pipe?
  6. Would a rear discharge floor mount toilet do the trick better so I don’t have to have a tower like throne?
  7. If I do a sink, where do I drain it? There is an unused capped 2” tee (I think that’s the word) into the drain pipe I think I could use.
  8. Wall mount toilets look like a hassle, but seem to afford the ability to make that straight shot into the drain pipe, but sometimes I see them on craigslist. Should I avoid like the plague?

Thanks again for any advice! Andy

Screen Shot 2021-12-04 at 10.12.12 AM.png

Screen Shot 2021-12-04 at 10.56.28 AM.png



Apr 30, 2014
Reaction score
Bloomfield Hills, Michigan
Yes your sanitary needs to be below the toilet unless you get a pumped set up, like saniflo. Does the sewer line go down below the basement floor over in the corner