Corner Sink Install

I'm renovating a small (OK, really small) full bath and have a question about the length of the tail piece for the sink drain. I have to install a corner unit because the sill plate of the only usable wall sits on top of a double joist in the basement and I don't want to carve it out for the water & drain lines. The old vanity consisted of a "custom built" cabinet (circa 1960) with the water and drain lines going straight down into the basment. Trouble is they sit about 18" out from the corner. Here's what I want to accomplish: install a corner pedestal unit with the water & drain lines tucked inside the pedestal so they can not be seen, and have the trap below floor level in the basement. Is this a viable solution? Any advice would be greatly appreciated.

No can do. Someone asked this last week.
There's a max limit on the tail length. I think it's 24 inches.
Anything greater will create too much head pressure on the draining water and will risk causing a siphon or pushing the water out of the trap.

Further, you can't put a trap just below the sink and then immediately transition to another vertical keeping the whole shebang somewhat tucked behind yr pedestal. Reason: it'll create an S trap, which has a high likelihood of siphoning the trap dry.

You have 2 options:

1) Go into the wall a few inches below the sink to create a short tail and a proper p trap (heck, you can tell everyone that horizontal branch is a 'towel bar'! )

or

2) install the sink 6-18" off the floor, drain under the floor, and call it a 'foot washer'

Gotcha! I can't go through the wall because of the double joist under the sill plate, so I guess I'll just have to use chrome and have the tail piece show behind the pedestal. Not really a big deal. Thanks for the input.

Can't you search for a corner vanity that'll allow you to use the old wall drain location?

1) Go into the wall a few inches below the sink to create a short tail and a proper p trap (heck, you can tell everyone that horizontal branch is a 'towel bar'! )

That is not enough to create a proper drain. All that does is make a different sort of "S" trap. It still needs a vent.

"That creates another type of S trap".

No it doesn't. That's not what I was describing. Read it back more carefully. I meant go into the wall like a "normal" perpendicularly mounted sink should, As long as the horiz portion is long enough going into the wall it won't be an S trap.

Would I still have the possible problem of siphoning in the S trap if I installed a P trap below the floor level? That's where it runs horizontal to the main waste line. The configuration would then have the S trap feeding into the P trap with about 18 inches separating them.

LarryK57 said:

Would I still have the possible problem of siphoning in the S trap if I installed a P trap below the floor level? That's where it runs horizontal to the main waste line. The configuration would then have the S trap feeding into the P trap with about 18 inches separating them.

Click to expand...

Without a vent between the two, I think so.... Maybe use one of those ventless doohickeys between the two?

trap

prashster said:

"That creates another type of S trap".

No it doesn't. That's not what I was describing. Read it back more carefully. I meant go into the wall like a "normal" perpendicularly mounted sink should, As long as the horiz portion is long enough going into the wall it won't be an S trap.

Click to expand...

The horizontal portion can be 12 feet long, but as long as there is no vent rising off of it at or before the point where it turns down it IS AN "S" trap. An "elongated S trap" possibly, but still an "S" trap. The "S" trap is in the construction, not the dimensions.