How would you vent & run water to the lavs in this basement bathroom?

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IndyGopher

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Installing large master bath in basement. Builders roughed everything in under the slab and I framed it and ran electrical. Was planning to hire the plumbing, but between the quarantine and plumbing estimates I got, I'm considering doing it myself. I posted a few questions here a couple weeks ago and got a few things figured out, but given my issues below, how would you vent and run water to the lavs in this setup?

1) Builder put a main HVAC trunk directly above lav 2. I dropped the ceiling to just barely below it, but I hadn't even considered plumbing at the time. Trunk extends out a couple inches on either side of the header, so I'm guessing any vents and PEX lines to lav 2 need to enter at some point without the HVAC obstruction and then run through the studs below it -- maybe even above the doorway.

2) I'm guessing everything is wet vented under the slab and only the lavs are meant to be connected to existing vents in the joists. There's one above lav 1 and another on the other side of the basement about 25 feet away from lav 2. I'm thinking both lavs can/should be vented by the one above lav 1, but again, the stupid HVAC trunk. Can a 1.5" vent line realistically be run through the framing above the doorway there to serve lav 2?

3) I was left 3/4" PEX stubs above the toilet and shower -- but nothing above either lav. There are 1/2" lines running in the joists above lav 1, I believe from the laundry room to the kitchen on the floor above. Would you tap into that 1/2" line to supply one or both lavs, or would you tee off one or both of the sets of 3/4" stubs that were left elsewhere in the bathroom?

Thanks for any advice!
 

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Terry

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For the bathroom water supply, come of the 3/4"
The 1/2" PEX for the kitchen sink and washer should not be tapped into. The 1/2" barely does them.
You can only run two fixtures on a 1/2" line, so a shower and a lav on a 1/2" line.
If you're running cold, then run the toilet off the 3/4" with it's own 1/2" line. You don't want someone flushing a toilet while you're in the shower sharing a 1/2" line.

One lav could vent with 2" and the second lav could vent with an AAV.
Or you could go over the header to tie them together.
 

IndyGopher

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For the bathroom water supply, come of the 3/4"
The 1/2" PEX for the kitchen sink and washer should not be tapped into. The 1/2" barely does them.
You can only run two fixtures on a 1/2" line, so a shower and a lav on a 1/2" line.
If you're running cold, then run the toilet off the 3/4" with it's own 1/2" line. You don't want someone flushing a toilet while you're in the shower sharing a 1/2" line.

One lav could vent with 2" and the second lav could vent with an AAV.
Or you could go over the header to tie them together.

Thank you, Terry! Couple additional questions if you or someone else would be so kind:

1) Since I've got 5 fixtures requiring water (cold only to the toilet, obviously), how would you share the four 3/4" stubs I was left (2 hot, 2 cold)? One cold obviously to the toilet. Should that cold be tee'd to one of the lavs with a hot -- both on 1/2" lines? That would leave the other stubs serving the shower, tub, and other lav.

2) I love the suggestion of an AAV. I don't know how everything is tied together under the slab. Would an AAV be an issue if that particular lav is wet venting other fixtures in the bathroom?
 

IndyGopher

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Just bumping one more time to see if anybody else would be kind enough to weigh in. I got some suggestions on other boards as well and feel ready to tackle this in the coming weeks, but just checking one last time. Thanks all! I've learned a ton reading this board.
 
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