Can I use the existing P-Trap for this bathroom reno

[closer]

our master bath reno is well on its way… all demo's have been done (and more as usual)… we are changing a 5'x8' bath room into a 8'x17' master bath. the photo shows the vanity wall in its stripped down mode… the notes show where we have planned on putting the new features, using as much of the existing plumbing as possible. I have a question with respect to the existing plumbing and how it fits with our new plans.

Left side of photo: My intent was to cut into floor immediately in front of the the old tub drain pipe and replace with a vertical section of ABS, run it up to form a new config including a P-Trap for the sink on that side. However the floor joists below preclude me from doing that. So, I can't find where there are minimum/maximum drops from the sink to a P-Trap and need your advise. As you can see we are building out (2x4 wall) two 32" sections of wall (left and right sides) to accommodate the wall mount Faucets. If I run a 90º elbow from the old tub drain (shown, lower left) then a vertical section up to the stone sink will this function? Pros and Cons? I imagine I will have to make it come out of the wall at some point so any suggestions for best practice would be appreciated as well. What type of joint would be best? a couple of 45º elbows?

The Existing left side P-Trap is 21" from the vertical run to the Vent stack. That vent stack will be about 7" - 8" from the bottom of the stone sink. At the far right of the photo is the 3" Waste Stack.

 

[hj]

None of your "ideas" for the sink drain are "legal" if I am understanding how you intend to do it. It is going to be a "weird" bathroom if the toilet sits in a shallow recess between the two sinks.

 

[Sponsor]

 

[closer]

I understand you probably don't like where the toilet is placed but sometimes we have no other options… having sketched this out however it works for us…

however, do you instead have a solution for making the left side sink drain legal? access is very limited due to the joists below… barely two inches clearance in front of the threaded ABS you see coming out of the floor in the lower left.

 

[Terry]

The trap for the sink can't be below the floor.
The trap arm for the sink should be on the same floor as the sink.
You can cut out some flooring, and replace the p-trap with a long turn 90. Bring it up and at 18" or so, you can add a santee for the trap arm. At 42" you can then go horizontal for the vent and tie into the existing vent.

 

[closer]

Thanks Terry… I figured there must be a way somehow…
There is a chance that I can cut enough of the bottom plate out (at the point where you see the 21" and to the right of the stud that is to the right of the existing bad trap) and then cut the drain at that point… if I can do that I think I could do as you suggest and put in a long turn 90 to bring it up vertically through the same hole, and the santee and then the PTrap to service that sink. depends on how close the copper is to the drain… and whatever else I find in there… it's been quite the discovery as I've opened things up!
I'm not sure I understand the 42" though as that would put me above the existing horizontal vent stack which is only at 36". Can't I just run my vent directly horizontal to that and replace the 90 that is there with a vent T? The base of the sink will be at about 30" when it sits on the counter top…

just added… I just checked and it looks like I'll be able to take out about 5" of the bottom plate and ply floor… the copper runs 6" below the level of the floor so there should be no problems with nicking that (famous last words!)… when I get to that stage is it necessary to run a long turn 90 or would a short 90 suffice?

 

[hj]

Since we cannot see ALL the piping, this is just a guess, but that vertical pipe should be the vent for the tub which is no longer being used so the sink can connect to it, assuming it has the proper fitting where it connects to the horizontal line.

 

[closer]

Since we cannot see ALL the piping, this is just a guess, but that vertical pipe should be the vent for the tub which is no longer being used so the sink can connect to it, assuming it has the proper fitting where it connects to the horizontal line.

Thanks HJ
The existing tub PTrap connects directly to the first vertical we see in the photo which appears to be connected with a vent tee to the waste line (previously for the tub but hopefully now for the left sink). Assuming I can replace the existing tub PTrap with a small length of ABS then with either a 90 or long turn 90, come back up through where the existing P will have been and then make the appropriate sink PTrap config, my next question would be:

Is it better to continue the vertical to approximately where you see the 32" line (parallel to the horizontal vent stack) or will it suffice to use the existing vent stack config as my vent for the left sink? The only difference is that with scenario 1 I will cut two more holes in the suds to push the ABS horizontal pipe through to connect to the existing horizontal vent stack.

 

[closer]

Here's a dry fit… not to correct heights as I am using parts that are available only… just for the idea… and there are three options… which one is both legal and the best option to ensure this functions properly, A, B or C?… sorry… C should read waste T, not vent T.

 

[Cacher_Chick]

The vent must be vertical until it at least 6" higher than the flood rim of the highest connected fixture.

 

[hj]

Seems like a lot of work when all you had to do was put a tee in the vertical line and run a pipe sideways in the wall to the sink's location, then cap the pipe where the old "P" trap was. You will have to cut the old elbow off so it will be too short for ANY tee without splicing in couplings and short pieces of pipe. Use a "combo" which is longer on both sides so it will fit once you cut enough off both pipes.

 

[closer]

Seems like a lot of work when all you had to do was put a tee in the vertical line and run a pipe sideways in the wall to the sink's location, then cap the pipe where the old "P" trap was. You will have to cut the old elbow off so it will be too short for ANY tee without splicing in couplings and short pieces of pipe. Use a "combo" which is longer on both sides so it will fit once you cut enough off both pipes.

ouch... wish I'd known that before... oh well... live and learn! anyway...

things have been cut already, so... which of the three scenarios in the photo would be best for me to follow... from what you have said, I should then be able to just use scenario B and go horizontal through the one stud to the vertical pipe (somewhere between the waste T near the new PTrap and the 90 on the existing vent stack?