Basement rough in plumbing questions

[ThatGoogleGuy]

Long time reader - first time poster. Thanks in advance for the advice!

I'm framing a basement for a friend. The house is only 11 years old, I'm impressed by the builders work, the entire house is plumbed with pex and has a very detailed manifold where practically every fixture is a homerun.

We assumed the roughed in plumbing for the basement bathroom was as follows from left to right - sink, toilet, shower. (pictures at the bottom)

• There is absolutely nothing plumbing related in the floor joists above the roughed in plumbing (figure this is worth pointing out because I have heard of builders capping off plumbing vent stacks in the joists so that you can connect to those in the future - that is not the case here).
• There is a sewer cover/access that appears to be in line with the roughed in fixtures.

My two questions assuming the rough ins are in fact for sink - toilet - shower

1. Would there already be a p-trap under the concrete for the shower drain?
2. Can someone refer me to a simple diagram to show how to ventilate the three fixtures with a cheater valve?

Thanks!

 

[Reach4]

Would there already be a p-trap under the concrete for the shower drain?

Yes. Pour some water in, and it will hold water that you could detect. That way you know which one is the shower/tub.
The 3 inch one is the toilet. The other one is the lavatory, which would wet-vent the others.

At least that's how it should be.

Can someone refer me to a simple diagram to show how to ventilate the three fixtures with a cheater valve?

2-inch Sanitary tee for the lavatory has the AAV at least 4 inches above the trap arm.

 

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[ThatGoogleGuy]

@Reach4 Thank you for the quick reply!

I will check tomorrow if it holds water - truly hoping the p-trap was already put in. I don't want to dig up any of the concrete.

Any chance you can point me in the direction of a wet-vent diagram for a setup like this one? I will look for one on google, but I'd trust your pick over mine!

 

[Reach4]

Here is Terry's diagram, which is intended for UPC. Yours would be the "3/4 bathroom" in the upper left.

IPC, which you are under, is a little more permissive. https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf page 12 shows a complex horizontally wet-vented bathroom group.

 

[ThatGoogleGuy]

So, because the drains are already connected to each other under the concrete, and assuming the p-trap is under the concrete for the shower - we wouldn't need to do anything aside from connect each fixture to its water supply and to its respective drain, connect the AAV to the lav, and we're good to go?

 

[Reach4]

That is your reasonable expectation. I am not a pro.

 

[Terry]

It looks like the lav will be venting the bathroom.
Either an AAV, or an atmospheric vent through the roof.
It looks like they planned it for an AAV.

 

[ThatGoogleGuy]

Thanks guys, I appreciate the opinions and advice!

I'll do some research on the AAV! It's usually fine to be installed in the vanity cabinet area right?