We are adding a prep sink to our kitchen. There is a 2 inch ABS vertical drain/vent pipe in the exterior wall of the house that is only a few feet away from the new sink that I want to tap in to. We have a two story house and this pipe vents and drains the upstairs bathroom sinks and possibly the bathtub. The vent then goes all the way up through the roof. The drain proceeds down through the cement foundation of the house.

At the base of the pipe just above the foundation is a tee with a clean out that opens to the outside of the house. I can cut the pipe above the clean out tee and attach a sanitary tee pointing through the wall into the kitchen and run the trap line through the back of the cabinet to the new sink. The problem is that the dishwasher is right where the pipe will come through the wall and there isn't space enough behind the dishwasher to run the pipe. But there is space behind the dishwasher if I run the pipe lower -- the tub of the dishwasher is six inches above the floor so I can run a pipe that low behind the dishwasher. My options are:

1) Raise the clean-out tee and put the sanitary tee for the new sink line BELOW the clean-out tee. Does code allow for the clean-out of the line to be above the connection of a trap line? If so, this will work for me.

2) Replace the clean out tee with a double sanitary tee. One side would connect to the trap line of the new sink and the other side would be the clean out to the exterior of the house. Can the clean out and trap line be connected through the same tee this way?

I have applied for a permit for this in conjunction with a remodel of our kitchen so it has to pass inspection. Any professional advice would be welcome!

Hi DCN...

I see no issue with installing cleanout above or below fitting for new sink. I also see no issue with installing a double sanitary TY fitting so cleanout and sink get piped in together... although I say you simply put a sanitary TY in below the cleanout for your purposes... no need for the double TY.. ok?

I have drawn up a basic drawing of the drainage/venting that is usually required by code for your setup (see picture). I may be off on location, but that doesn't matter, what matters is how all this connects together... bear with me... ;).

You can see that I piped up a tub and 2 sinks on 2nd floor... I included waste piping and vent piping.. all drawn in red. I also drew in the proposed sink waste and vent at first floor, but I drew the vent in blue to emphasize how it must run UPSTAIRS, parallel to the 2" waste stack and it must connect into a vent pipe at least six inches higher than the top of the lavatory UPSTAIRS to be vented BY CODE. That is only way that you can do this by code... UNLESS, your inspector will allow air admittance valve (AAV).

An AAV is a mechanical vent that is installed at the point of use.. under the sink cabinet in this case... and it could eliminate the need to run that 1.5" vent upstairs to connect it into the vents upstairs.

Unfortunately, these are illegal almost everywhere that I know of... :(

Check with your local plumbing inspector and ask him if AAVs are allowed... if so, YOU LUCK OUT! Pop back and we will explain how to install it.

If no AAV allowed then you have no choice but to pipe all this as I described OR find another alternative... ok?

Let me know what you need... what you're thinking.

MARK

Mark,

Thanks for the quick and thorough response. I don't know all that much about plumbing but I like to learn things and do them for myself. This is a bit more complicated than I thought but at least now I know what I need to do. Thanks for taking the time to answer and draw up that plan!

Glad to help DCN...

Let me know if need more.