Going from Single to Double Sink in Bathroom Vanity

[Ron Katcher]

Just doing some initial research now. Our upstairs bathroom currently has a single sink and I would like to know the extent of the work necessary to replace the existing vanity with a larger one that will accomodate two sinks. Can supply and drain lines be run connected to the existing lines that are there for the single sink (essentially creating a "Y" with each of the existing lines, with each drain having its own trap) or will this job require separate plumbing runs further into the system?

[Speedy Jim]

I would use a double WYE 1 1/2". That will give you a branch in each direction plus a CO plug in the center. Use a 1 1/4" trap adapter at each branch inlet for the traps.

It's also possible to use a single 1 1/2" trap with a "center outlet" TEE assembly (commonly used on double bowl kitchen sinks). A special reducing washer will accomodate the 1 1/4" sink tailpiece into the 1 1/2" TEE assembly. If the bowls are too far apart, use the 2 traps instead of this method.

Jim