Every time the washing machine drains the dirty water backs ...

[peach]

Every time the washing machine drains the dirty water backs up in my kitchen sink (it`s between the washer and main sewer line) I recently noticed that there is no vent pipe in the roof above the laundry room. Would that fix the problem? I`m getting tired of bleaching the kitchen sink whenever I do laundry.

[yeibiche]

Can you see the waste pipes that serve your Washing Machine and Sink? If it's plastic, you should be able to read the size on the side. It should be a minimum 2" line. If there is no vent on the washing machine waste, that could definately cause a problem, the air getting pushed ahead of the pumped water has nowhere to go in a hurry, causing your flow to slow down.
Also, you can get some improvement by putting a 24" standpipe out of your trap and cuttin in an automatic vent right there. I haven't figured out how to send an attachment or I'd give you a quick schematic how to. (based on PVC pipe, CI or copper is a bit more complicated.

[peach]

Thank you yeibiche. The drain pipe for the washer is not really visible. There is a pipe where the machine hose goes but it's a strange angle and I can't tell where it goes. The kitchen, all that can be seen is the drain pipe under the sink and it disappears into the wall. Whatever the pipes look like beyond the wall is a mystery. I thought that by extending the drain pipe for the washer and putting on a hose for the air might work but, I would have to cut into the wall to do that. Do you think a "Y" would work if the end of the machine hose was higher than the point where they meet?