Single to double lav drain and vent help

[dadamw8]

I'm looking for the easiest and best way to make this single lav waste/vent setup into a double. The current trap adapter is in the center of the wall and the new vanity setup will have an 18" drawer base cabinet in the center and a 30" sink base on both sides of that. Which would make my trap adapters need to come out right around where the two visible studs are at in the corners of my wall and picture (16" off corners roughly). I can handle cutting and heading off the framing and running the pex but I'm unsure about the best way to plumb the new double lav drains and vent. I'm in VA as far as codes go. Thanks for the help!!

 

[James Henry]

Your question is kinda vague. Take a magic marker and draw on the floor where the sinks will be located and you'll get a million replies.

 

[Sponsor]

 

[dadamw8]

Your question is kinda vague. Take a magic marker and draw on the floor where the sinks will be located and you'll get a million replies.

Sorry about that!

Sinks will be where I put the red lines on this Pic. Basically in the corners where those last visible studs are.

 

[dadamw8]

Also if it helps any. This bath is on the second story over a garage. The 1.5" pvc is ran through the wall and steps up to 2" inside an attic area over the front porch. Hopefully the pics help this make sense!

 

[plumb1234]

You could try this, if it won't be too high for your sink. Also, make sure it's not a load bearing wall before you go bore through those studs.

 

[wwhitney]

Virginia uses the IPC, which is flexible and allows both common venting (trap arm, trap arm, single dry vent takeoff) and wet venting with a 1-1/2" drain carrying 1 DFU (trap arm, single dry vent takeoff, trap arm). So you don't need to have two separate vent takeoffs, or raise one of the trap arms (other than the necessary 1/4" per foot slope for horizontal drains).

But the important question is whether the lav drain is being used as a wet vent for another fixture, like a tub, shower or WC. If it is, and if you add another lav to the wet vent, then the drain size needs to be increased to 2" as soon as the second lav joins.

Cheers, Wayne

 

[dadamw8]

Virginia uses the IPC, which is flexible and allows both common venting (trap arm, trap arm, single dry vent takeoff) and wet venting with a 1-1/2" drain carrying 1 DFU (trap arm, single dry vent takeoff, trap arm). So you don't need to have two separate vent takeoffs, or raise one of the trap arms (other than the necessary 1/4" per foot slope for horizontal drains).

But the important question is whether the lav drain is being used as a wet vent for another fixture, like a tub, shower or WC. If it is, and if you add another lav to the wet vent, then the drain size needs to be increased to 2" as soon as the second lav joins.

Cheers, Wayne

Everything is else is vented separately, but I'm unclear on exactly what you mean... So are you saying that according to code. I can just continue my 1.5 run to secund sink and not have to add another vent as long as I get my vent in front of the first sink in the run?

 

[wwhitney]

So are you saying that according to code. I can just continue my 1.5 run to secund sink and not have to add another vent as long as I get my vent in front of the first sink in the run?

IPC Common Venting would be this pattern in the wall, going downstream: horizontal LT90 (upstream most lav) - horizontal combo (second lav)- dry vent takeoff. Each trap arm gets measured from the trap under the sink to that vent takeoff, and each one must be at most 6' of run and at most 1-1/2" of fall.

Wet venting would be this pattern in the wall: horizontal LT90 (upstream most lav) - dry vent takeoff - horizontal combo (second lav). The trap arm for the upstream lav is from the trap to the vent takeoff; the trap arm for the second lav is from the trap to the horizontal combo. Again, each one is at most 6' of run and at most 1-1/2" of fall.

Cheers, Wayne

 

[dadamw8]

IPC Common Venting would be this pattern in the wall, going downstream: horizontal LT90 (upstream most lav) - horizontal combo (second lav)- dry vent takeoff. Each trap arm gets measured from the trap under the sink to that vent takeoff, and each one must be at most 6' of run and at most 1-1/2" of fall.

Wet venting would be this pattern in the wall: horizontal LT90 (upstream most lav) - dry vent takeoff - horizontal combo (second lav). The trap arm for the upstream lav is from the trap to the vent takeoff; the trap arm for the second lav is from the trap to the horizontal combo. Again, each one is at most 6' of run and at most 1-1/2" of fall.

Cheers, Wayne

Thanks for your help Wayne! So if I'm understanding you correctly with my limited plumbing knowledge, then this should work, right??

 

[wwhitney]

That works for wet venting the right hand lav with the left hand dry vented lav, with nothing further wet vented downstream. The fitting on the right for connecting the right hand lav should be a combo, not a san-tee on its side (can't tell from the picture). The horizontal segment of dry vent needs to be at least 6" above the lav flood rims.

Cheers, Wayne

 

[dadamw8]

That works for wet venting the right hand lav with the left hand dry vented lav, with nothing further wet vented downstream. The fitting on the right for connecting the right hand lav should be a combo, not a san-tee on its side (can't tell from the picture). The horizontal segment of dry vent needs to be at least 6" above the lav flood rims.

Cheers, Wayne

Thanks Wayne, appreciate your help. It's a combo wye and the horizontal vent is at 43" so I should be good! Thanks again!!