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How would you vent and run water in this basement bathroom?

4 years ago

Homeowner here. Finishing a large basement, including a big master bath. Builders roughed everything in under the slab, and I framed it and am running electrical. Was planning to hire the plumbing, but between the quarantine and plumbing estimates I got, I'm considering doing it myself. I've posted a couple photos and will describe my issues below. Would appreciate advice and how you'd vent and run water to the lavs in this setup. Thanks!

1) Builder put a main HVAC trunk directly above lav 2. I dropped the ceiling to just barely below it while framing, but I hadn't considered plumbing at the time. Trunk extends out several inches on either side of the header, so vents and PEX lines to lav 2 can't come straight down. Either they need to run through the framing on either side or I need to frame a bulkhead on the wall behind the bathroom. That area is like an entryway or sitting room with entrances to the master bedroom, bath, and a closet.

2) Builders left a capped 1.5" vent above lav 1 and another on the far side of the basement about 25 feet away -- perhaps for lav 2. It's near the ejector pit, but that already has its own capped vent left on the wall right next to the waste line. Can both lavs (and by extension, the whole bathroom -- two lavs, toilet, and separate tub and shower drains) be vented by the line above lav 1? Either way, how would you deal with that stupid HVAC trunk above lav 2? Can a 1.5" vent line realistically be run through the framing above the doorway there to serve lav 2...or is a backside bulkhead a better idea?

3) Builder left 3/4" PEX stubs above the toilet and shower, but none above either lav. There are 1/2" lines running in the joists above lav 1, I believe from the laundry to the kitchen on the main floor, but no stubs left. 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? And again, given the obstacles around lav 2, how would you run those lines? Parallel to the vent after figuring that out?

Thanks for any advice!

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