Basement underground and vent plans for 2 baths and kitchen.

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Well-Known Member
Oct 25, 2013
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Hello all. I know there are numerous ways to pipe and vent this, but this is what I have and paid for, so I would appreciate if we don't veer off course too much, but rather build from what is here. I am here because I want to know if there are any errors or concerns with this plan before I start digging or paying a professional to do so, because I don't want to eff this up.

- Purple = 3"
- Orange = 2"
- Green = 1.5"
- Solid colors are drains
- Dotted colors are vents

1) Will this vent plan work well as is?
2) Will this drain plan work well as is?
3) I have a concern about the two double 3" wyes. I know that a double wye fitting for back to back toilets are a no no, but in this case, is it ok since they are piped very differently?
4) In regard to the right-hand bath shower vent. The underground 2" tee for its vent is on its back looking up and the plan is to street 90 out the top and make my way over to the wall and then up again. I heard you can't go horizontal with a vent until above flood level rim, but plumber says not true in this case. Is this correct? If not, is it really the end of the world to leave it this way?

Thanks guys.


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Your plan seems generally sound, but it's crucial to address potential issues beforehand:

Vent Plan: Appears reasonable, but ensure adequate venting for each fixture.

Drain Plan: Size selection should be sufficient, but ensure proper slope and avoid sharp bends.

Double 3" Wyes: Unique configuration may work, but consult a professional to confirm.

Shower Vent: Verify compliance with local codes regarding horizontal venting below flood level rim.

Consulting a professional plumber is advisable to ensure everything meets safety and regulatory standards.
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