Hello all,

I have plumbed two bathrooms for myself in the past 20 years and both times I ran into drain and venting issues with the inspector. I eventually passed my inspections but for me what logically makes sense will work doesn't seem to past the muster test with the plumbing code. I have been asked to help a neighbor with his basement bathroom plumbing so I want to make sure I give him sound advice.

He currently has a room in his basement with only a toilet. He would like to add a shower and a sink to the room to turn it into a fully functional bathroom. I have attached a sketch of what I think will work for the waste and vent lines, but based on my past experience I am not so sure. I have looked at a lot of waste and vent sketches online but none of them seem close enough to my sketch to give my any confidence.

In addition I have one question at the moment:
1. Do the lines that tie into the 4" cast iron drain leading to the stack have to drop waste in from the top or can a drain line tie into the side of the 4" c.i.? I ask this because the top of the 4" c.i. is 4" below the top of the slab. With a 4" slab there is no room above the pipe for any other plumbing.

Thank you in advance for giving me insight on the attached drain and vent sketch.

Blane

 

I understand... I've been doing this a while and still run into DWV designs that aren't quite right in my mind.

I believe you're close.

* You don't need the shower vent. The existing vent will work fine (as long as it's within 16 feet)
* Unless there's some other reason, I would make the sink drain more direct and tie into the main drain between the shower and toilet.
* The existing toilet vent could be replaced by the sink drain/vent (if upgraded to 2"). No issue with leaving it as-is if you'd rather.
* No issue with tying into the main drain on the side. Use wye or combo-wye fittings regardless.

 

Zorfdt,

Thank you very much for the feedback. The reason I show the sink tying into the 4" c.i. further down the line is that the 4" c.i. is right below the slab. I don't believe I would be able to slope the sink line at 1/4"/ft and have it high enough to tie into the side of the 4" c.i. What I have tried to show in the sketch takes the sink drain line through the studs (although you can't tell this from my sketch) and drops it into the concrete where the 4" c.i. will be slightly lower.

Thanks again, I really appreciate it.

Blane

 

Unless your neighbor already has a bath exhaust fan he will probably need one for the inspection.

 

Yes, exhaust fan needs to be installed. Thanks for the reminder.

Blane