I am redoing my bathroom and exposed the ceiling to see the upstairs plumbing from below. I found a trap in the floor for my upstairs vanity sink hidden in floor. The vanity also has a s trap located inside the actual vanity which can be seen by just opening the doors. I see no venting at all. It tee into the tub waste line and drops two floors to join into my 4 inch main waste line. What should I do. I only have the down stairs bathroom open and can get rid of the hidden drain and then replace the s-trap with a p-trap. But then I don't know how to vent.

Hi Jjsttinia:

Best thing to do here will be to remove both traps and then install a PTRAP and a mechanical vent (AAV... air admittance valve)... see pictures.

The AAV needs to be installed about 6 inches above the trap... can be located on vertical (1st pic.) or on the horizontal (2nd picture).

Although not "code legal" in most places the fact that your sink had no vent suggests that this is a very good chance to improve on the inferior design in place now... ;) It may even improve draining of the tub... certainly can't hurt.

AAVS thread into female adapters... can use 1.5" (black AAV below) or 2" AAV (white/blue)... sold at all home improvement stores.

Let me know if you have any questions...

MARK

Hi Jjsttinia:

Best thing to do here will be to remove both traps and then install a PTRAP and a mechanical vent (AAV...air admittance valve)....see pictures.

The AAV needs to be installed about 6 inches above the trap...can be located on vertical (1st pic.) or on the horizontal (2nd picture).

Although not "code legal" in most places the fact that your sink had no vent suggests that this is a very good chance to improve on the inferior design in place now....;) It may even improve draining of the tub...certainly can't hurt.

AAVS thread into female adapters....can use 1.5" (black AAV below) or 2" AAV (white/blue)...sold at all home improvement stores.

Let me know if you have any questions...

MARK


Thanks for this, this is what I was thinking but wasn't sure and didn't know the "rules". Thanks, this sounds like the best plan for me in leui of a true vent tie in, which is not possible with out major work.

Go back and check the other question now... I revised my answer and drew a picture for you! Let me know if need anything else. I'll be back on later this afternoon.

MARK