Hi everyone, happy new year. I am planning on adding a small, full bathroom in the corner of the basement. There is an existing sewage ejection pit for the floor drain and I plan on breaking out concrete and tying into it with a 3" PVC waste line.

I want to be sure the plumbing is vented properly. One existing wall is rough framed against the poured concrete wall and I can go up through the wall upstairs above the kitchen sink, behind a cabinet, and tie into that vent for the basement and not have to make a finished repair of the drywall.

The shower is a 3' X 4' across the furthest end and the drain would be 8 1/2 ft., away from the pit, next a sink, then the toilet would be 33" from the edge of the pit to it's center. One challenge is that nothing is in a straight line and I don't think I should tear out the rough framed wall and break out a trench next to a poured concrete wall. I thought I should run the line straight from the pit to the toilet and on past in a straight line until I can intersect the shower drain at a 45 degree, horizontal angle. Between the 45 el and the toilet I could use a horizontal Y to branch over and up through the wall for the sink drain and on up and then over to tie into the vent from upstairs. I would also vent the (unvented) pit with that same vent.

Would everything be wet vented properly? Where should I reduce the 3" line for the shower P trap and sink? I have attached 2 scale drawings to show the location of the planned drains and my proposed layout of the waste line and trench.

Isn't there a rubber gasket made to install in the hole I make in the pit wall for the 3" waste line? Should it be silicone caulked also or pour concrete around that joint when I cover the excavation?

I would also vent the (unvented) pit with that same vent. You can't do that. To operate correctly the pit MUST have its own dedicated vent, Because the pit vent both vents the pit and expels air out of it you MUST not connect back to any house vent. The lav vent may reventback to a existing dry vent at least 6" inches over the flood rim of the fixture that you're reventing back to. Because of the pressure produced as the fixtures discharged into the pit and the suction produced as the pit empties the connection to the pit MUST be air tight. Is there any way you could cut into a existing 3" pit drain? Regards, Tom

Thanks for getting back with me, Tom.
There is only a 2" floor drain (from across the basement) into the pit appearing to be sealed with silicone and feels like concrete against the pit wall surrounding it.

I can run a dedicated pit vent straight up and over 3 1/2 ft. through an outside wall and turn up with a snorkel vent terminating a couple of feet above ground level. The pit lid will seal and has a rubber gasket for 1 1/2" vent pipe and a 2" rubber gasket, which I could use for the sink drain, since its' trap would be above the floor level, but would that make the wet vents for the shower & toilet to far away?

If the pit has a grinder pump to precess sewage it should also have a 3" inlet for a toilet drain line. Your shower appears to be wet vented by the lavatory vent. Can you give me the name of the system that you have? Your pit vent will be acceptable to install by my code book. Good luck, Tom

I just added a Wayne 1/2 HP cast iron 2" sewage pump and a Topp Industries lid for the pit, that screws down and has rubber bushings for power chords and pipes. I'm not sure the brand of the black, plastic pit, but the lid fits well. The pit also was used for a washing machine and that waste entered from 2" plumbing through the lid. Does this answer the question about what system I am using?

Does my proposed layout seem OK? Would everything be wet vented properly? Where should I reduce the 3" line for the shower P trap and sink?