Can I plumb a washing machine drain into an existing bathroom sink drain?

Question

I am installing a washer and dryer on the second floor of my home. The location is right next to a bathroom, so my idea is to run a flexible drain tube through the wall and connect using a Y fitting to the sink drain. The units are newer Maytag units, and I'm just wondering if the pressure from the washing machine unloading its water would cause the sink to overflow?

Answer 1

Yes,
You can use the drain pipe that s inside the wall, but not the stub out pipe to the sink. This is a job for a plumber. Good Idea putting units on 2nd floor. Saves a lot of steps. Don't forget to put your washer in an emergency overflow drain pan. Just in case it ever overflows the drain it won't ruin your ceilings. Good luck

Answer 2

If you were to do that you would have to put the standpipe for the hose into a section of pipe that has a drain trap between your connection and the vertical drain pipe. Otherwise sewage odors will come up and fill your room with toxic explosive gases.

If you have a large basin you can just let the drain pipe go into the basin. However that will look tacky and the basin volume and rain rate must be less than the discharge rate of the washing machine or it will overflow. Even worse if it is marginally adequate the buildup of lint from the esdher discharge will eventually make the drain slow enough that it will overflow. The issue is not pressure - it is gallons per minute flow rate out.

Answer 3

Don't do it. The plumbing codes for washer drains has been changed to using 2" pipe instead of the old 1-1/2" drainlines. Reason is that the newer washers have more powerful pumps and water will back up and overflow. The standpipe for the washer drain also needs a trap installed.

Answer 4

You should be fine, just allow the for a good degree of fall in the waste pipe from the washing machine so all the waste water drains away. Just be aware of using the washing machine and the the basin at the same time as to much water going down the drain at the same time may overflow.

Answer 5

I would plumb it back into the 1 1/2 drain in the wall not into the acctuall under the sink plumbing and dont for get that your drain hose has to stay up above the water level of the washer dont just take the drain hose straight out and level to a drain line if you are worried about back presure you can install a check valve ( one way valve ) at the sink but on a normal washer hook up the hose just sits in the drain hole and water never backs out of the space around it

Answer 6

Yes,
Bad idea.
As a matter of fact, I have a service call next week where a washer drains into the lav riser. It backs up into the lav bowl, and overflows onto the floor.
They want me to see what I can do to stop that.

Answer 7

not if the sink drain is the same size as the washer drain,

Answer 8

not legally. I still wouldn't do even if you don't care about it being right because it will not work properly. You need to pipe it into a 2 in drain.