I want to put a washing machine in my kitchen and tap into the drain under the kitchen sink. The existing drain is 2'' pvc. Should I add a y connection before the p trap for the sink and not have a p trap for the at the bottom of the standpipe for the washing machine or should I connect into the existing drain where it runs horizontally after the sink p trap and have a p trap at the bottom of the washer standpipe?

PMCGRAIL:

You want to hook in after the sink ptrap and vent... ;) Here, you will want to cut into the pipe and add a 2" wye fitting to pick up the washing machine drain.

Install a 2" PTRAP at the washing machine, a mechanical vent (AAV) and a standpipe about 30" tall if possible....see picture below. The AAV is required so that the washing machine PTRAP doesn't get siphoned when the kitchen sink/disposal/dishwasher drain past the connection for the new washing machine drain.

AAVS are sold at all home improvement stores...see picture. You will need an 1.5" threaded female adapter and some pipe dope to install the AAV into the PVC. This also suggests that you will need to reduce the 2" pipe using a 2"x1.5" PVC coupling and then install an 1.5" STREET female adapter for the AAV and you won't need to buy any 1.5" pipe... ;)

I also included a 2" dandy cleanout (also called a test tee) in the drain line. These are always a good idea... just in case. The cleanout at the PTRAP is a requirement where I come from.. in case something gets caught at the trap itself... although almost never happens with PVC.

Let me know if you have more questions...

MARK

Thanks fro the reply Mark

The only problem I see is I can only connect to the horizontal pipe right after the sink p trap. The horizontal pipe goes into a wall and I don't know where the vent stack is for that drain. I know it doesn't go straight up because it is under a window and there is only one vent going through the foor for the bathroom and the kitchen. I am also on the 3rd floor of a condo. Can I connect into the horizontal drain pipe before it goes into the wall but afterr the sink p trap?

Something like this

I'll jump in : In this case, connect into 2" horizontal pipe after sink's p-trap. Install AAV vent. Yours revised drawing looks fine...

I undertand you don't have too many options to connect to. But please, be aware that you are connecting sink drain ( most dirtiest drain in house ) to washer drain ( drain with most rapid volume discharge ). I would suggest to install a lint sock on your washer stand pipe and be judicious in using garbage disposer. If you use GD a lot, than make sure you flush it with lot of water after each use.

Luckily there is no garbage disposal, Can I use a tee connector in place of the Wye, I have very limited space and would need to have a couple of 90 degree bends and a 45 to the wye? A tee would need on 2 90'S

You need a fitting that will transfer water to your kitchen sink drain as fast at possible. Y fitting is that fitting. T fitting will slow water flow, making it to back up into your stand pipe and eventually overflow it.

It is easy, and cheap , to rework your kitchen drain under the sink to accommodate new T.

Hi guys:

I'm never really sure how to advise in these cases.

The fact is that this is a condo... many rules usually apply. Most condos require that permits be pulled for any work performed inside the building... otherwise you can be found liable for damages that result from say... washing machine overflowing as an example. Then, to install this against code... connecting into kitchen sink drain before the vent... hmmm... like I said... don't really know how to advise when this happens.

I would really prefer to see PMCGRAIL find the horizontal pipe and connect into that after the sink vent... a plumbing inspector would certainly make him.. ;)

Up to you... I just wanted to be clear that the way you drew it is illegal. It will work, I'm sure... but not right!

Either way... use SS braided hoses and be sure to install a single lever shutoff for the water and actually use it after each load (why they make these valves). That should reduce most of the chances that you will have any mishaps...

Anyway... just my thoughts all...

MARK

I am trying to hook up the drain from my washing machine not the drain of my bathroom sink, the drain for the sink goes into the wall after the U joint could you please advise me as the best way. I am also trying to hook the water to the washer?