Please review the piping plan for basement remodel

Hey everyone, we’re starting to remodel a basement in our house that is 90+ years old. We’ve read many, many, many posts on this forum, hoping to educate ourselves.

The existing 3†soil pipe is above ground where we want to put the new bathroom (which is below the first floor bathroom). It does enter the ground across the room.

To avoid using a swage ejection pump, we are planning to trench across the basement until we meet the existing soil pipe under grade. We’ll probably have to use 1/8th inch over 12†pitch to meet up with the existing soil pipe. The new 3†pipe will be approximately 30 feet long, and will meet the existing soil pipe which is 4.5†below grade.

The new basement toilet, lavatory, shower, and washing machine will drain to this new pipe, and the vents will connect to the existing vent that the first floor bathroom uses. I have the shower and the washing machine sharing a vent, not sure if that is allowed.

Can you please review the piping plan for any glaring mistakes? (see 5 images below). Please assume that all drain pipes will be pitched at ¼ inch over 12â€, and the vents will be pitched so that they will drain back to the drain they are venting. (Modeling the pitch was very difficult, so I gave up on it!). You’ll see several wye’s that are on their sides, assume they will be canted upwards to gain the required pitch. (Again difficult to model).

pipe

What difference does it make whether the pipe is 40 or 45 degrees as far as the depth is concerned. IF the pipe is NOT at a 45 degree angle, your other fittings will not line up properly. If the sewer is only 4 1/2" deep, it is too shallow to make the connection to the toilet. You are connecting to a DRAIN line, not a vent by the tub and can absolutely NOT DO THAT, and the downstairs shower is not vented.

If the drain line was 4", you might be allowed to use 1/8"/foot. Sounds like you need an ejection pump, UNLESS, you can run the line outside the foundation and find a place low enough that will allow you to provide the needed slope. This might be a good ways towards where the existing sewer line meets the main for the neighborhood. This is typically below the frost line, and could be much deeper than that.