Advice on venting basement bathroom

[Michael Berry]

I'm in the process of planning my basement bathroom and am curious about opinions on how to best handle the venting.

I'm in Michigan and follow IPC 2012.

The bathroom will consist of a water closet with a 3 inch drain, wet vent through a lavatory on a 1.5 or 2 inch line. This will then continue through a backwater valve and finally tied into the 4 inch building drain.

Here are the options that I am considering - I'm not sure what is best and what is/isn't allowed.

1) Directly above the basement bathroom is a first floor bathroom. The 1st floor toilet wet vents through the 1st floor lav and the lav's 1.5 inch vent goes up to the attic where it ties into a vent from a 2nd floor bathroom and then out the roof. Would I be allowed to run the basement bathroom's vent up through the wall and then tee it into the 1st floor bathroom's vent 6 inches above the flood plain of the first floor bathroom? This would allow for an atmospheric vent with relative ease. I think I'd be within the 42 feet developed length of the vent, but would need to make sure. Also, I believe I'd be limited to a 1.5 inch drain in the basement, as I'm guessing it wouldn't be allowed to reduce from 2 to 1.5 when tying into the first floor bathroom.

2) Run the vent from the basement all the way up to the attic. Could go with a 2 inch drain in this case.

3) Vent the basement bathroom with an AAV. If I went this route how would I go about doing a leak test for an inspector - specifically how to put 10 feet of water in the system when the system doesn't go 10 feet high?

Thanks!

 

[Stuff]

I vote for #2 as things work best with a real 2" vent. Important if you are intending to use the bathroom.

What's going on that you need a backwater valve?

 

[Sponsor]

 

[Reach4]

backwater valve

Don't get a flapper valve with a normally-closed gate that hangs down. They will not seal when needed. Normally-open type work more reliably.

 

[Michael Berry]

I vote for #2 as things work best with a real 2" vent. Important if you are intending to use the bathroom.

What's going on that you need a backwater valve?

Nothing going on per se, just code compliance with IPC 715.1 as it requires a backwater valve to protect basement fixtures as they are below the nearest upstream manhole cover.

The big downside is I'll have to have an access cover in the bathroom floor that I'd prefer not to have, but given space constraints there is nowhere else to put it.

As for the suggestion to get a normally open - I'll take a look. A quick search turns up one made by Mainline, but only available in 4 inch from what I can tell. I do like the idea of it being normally open. Thanks for the advice!