I have a utility sink in my garage and no way to tie into a vent stack. It has a trap underneath it, and drains through the wall and down into the basement, a drop of about 8 feet. It makes a 90 degree turn and slopes down to a floor drain about 20 feet away. Right after the 90, I have a water softener drain line tied in. It runs about 8 feet on a 30 degree angle. My question is this. Do I need to use an Air admittance Valve under the sink or can the water softener drain line serve the purpose?

Thank you.

are you saying that the sink drains dumps into the top of a floor drain with no direct connection to it ?

If I understand your question regarding the Air Admittance Valve portion, I think it would be a good idea. As for connecting to a water Softener drain I would need to see a drawing for more details.

If it just dumps into the floor drain, then it is NOT connected to the sanitary system and does not need a vent.

That is correct. Thank you. You answered the question.



Edited 1 times.

That's the way I understood it Packy. Question: Does the garage sink still need a trap, since the floor drain is already trapped?

- - - - - - -

Not a plumber by trade but a fierce DIYer



Edited 1 times.

No, waste should only have one trap.



Edited 1 times.

it will have only one trap.



Edited 1 times.

LI guy, the only reason to have a trap would be to keep back the odors that might come from a long pipe that could get fouled from whatever gets poured down the sink.
other wise this is considered an indirect waste and no trap needed.



Edited 1 times.