[papa_pilot]

I have a question about a sink drain line that I am installing. Specifically, do I need a vent for the new drain line? The following are the details of my situation. Please bear with me as I want to give you a clear picture.

I recently put on an addition next to my kitchen and in that addition I want to put in a new bar sink. The only place I can tie the bar sink drain into is the kitchen sink drain pipe as there is no other plumbing on that side of the house.

The kitchen is above a crawl space. I have clear access to the kitchen drain pipe which runs vertically from the kitchen floor to the cement crawl space floor. The kitchen drain pipe is 1 1/2 in and there is a clean out fitting right before the drain pipe enters the cement floor. The horizontal distance from the kitchen sink trap to the point where the waste line enters crawl space the floor is about 6 inches.

I have tried to verify that the kitchen drain is vented but I cannot find one. There is no vent line coming out of the roof above the kitchen. I have looked in the attic but did not see any plumbing above the kitchen. Furthermore, there is no other plumbing on that side of the house so the likelihood that the kitchen is vented to an existing vent line in the wall is unlikely.

The main stack enters the crawl space floor about 25 feet from where the kitchen drain pipe enters. I assume the kitchen drain ties into the main stack under the cement floor but I have no idea how long the kitchen drain runs until it ties into the main stack.

As for the new bar sink drain, I would like to tie it in to the kitchen drain pipe about 16 inches above the clean out fitting. The horizontal run for the bar drain would be about 11 feet and there would be a vertical drop of about 3 - 4 feet from the bar trap to the tie in point. I was going to use 1 1/2 in pipe. I can easily run a vent line through the roof from the point where the bar sink drain enters the wall.

Should I install the vent on the new drain? Would having this vent affect the performance of the kitchen drain as it would now be vented below the trap? Would this new vent affect the performance of any other drains in the house?

And, beyond the vent line, is it okay to tie the bar sink drain into the kitchen sink drain line? Would it be more appropriate to use 1 1/4 inch pipe for the bar sink drain so that it is one size smaller that the drain pipe it ties into?

Thanks for your advice.
Andy

[21boat]

Basically all sinks or bar or what ever requires a 'P" trap and NOT a 'S" trap. The 'P' trap setup is the connection in the wall is a T fitting and the bottom of the tee goes the drain waste. The top of that tee starts the vent which ties into another vent over head or connects to another sink overhead vent and all vents go up trough house and out roof. Any added vent stacks is a big plus and may help the mian line on hook up.

Signed 21 boat

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[Milo Dolezal]

In this situation you should install at least AAV vent inside the Bar sink cabinet. 11' is a long run.

There is no 1 1/4" drain. You will have to use 1 1/2".

[21boat]

There is a 1 1/2 to 1 1/4 desankos couplings that reduces any 1 1/2 PVC to accept 1 1/4 sink drain lines. There's also a (cheater vent)thats made to vent a tough spot like a center bar but in my area they are a code violation

[Milo Dolezal]

There is a 1 1/2 to 1 1/4 desankos couplings that reduces any 1 1/2 PVC to accept 1 1/4 sink drain lines. theres also a (cheater vent)thats made to vent a tough spot like a center bar but in my area they are a code violation

Those 1 1/4" drains are Tubular Drains. Basically, it is trap and trap arm. Some 1 1/4" extension can be used - but not 11' long run.

[mike mantia]

How to tie drain to stack show picture