Modern Pedestal sink P trap thru floor

[Doug Westbrook]

Help! My junker wife came home with a used Hometek pedestal sink and wants to replace an old vanity sink in the bathroom. I realize I have to move the plumbing and it has to look nice. I've got the supply lines figured out but cannot figure out how to install the P trap to the drain in the floor. I cannot move plumbing to the wall. There is a hole in bottom of pedestal that is lined up directly under the sink drain. (I am assuming it is for the drain pipe...) How do I have a P trap line up in a straight vertical line??

 

[Reach4]

You want the sink to drain into the floor drain rather than connected to the drain plumbing? If that is permitted, I don't think there would be a P-trap other than the one that the floor drain already has.

I am not a plumber.

 

[Sponsor]

 

[Jadnashua]

Canada seems to allow a p-trap to be below the floor, but none of the codes I'm aware of in the USA allow it. If your drain now goes into a p-trap, then the outlet of that goes down through the floor, you have an illegal S-trap. Changing things would require coming up to current code, which would mean getting your drain into the wall along with a vent. S-traps were used on older buildings, but they have not been legal on new or remodels for many decades.

There's probably not enough room to plumb in an AAV (if they are even allowed where you live) to emulate the proper atmospheric vent - there's usually just not much room behind a pedestal sink.

A picture of what you currently have may help clarify the situation.

 

[Smooky]

 

[Jadnashua]

If you have room, and an AAV is allowed, it would convert things to a proper p-trap from an s-trap that I think is what you described (can't tell for sure without a picture). Not all places will allow an AAV, then to get it right, you'd have to tear up the wall behind for the vent/drain.