Sewer smell from laundry room

[Ken New]

I think the washing machine forces water down the drain pipe so fast, that it siphons the water out of the trap. Is this possible and if so, how do I fix it.

The laundry sink is in an adjacent cabinet. The washing machine drain pipe attaches to the sink drain above the trap, so the trap is shared by both the washing machine and the sink. It is 1 1/2" ABS plastic pipe. The washing machine drain falls vertically for about 16"and then horizontal for 30" into a TY fitting directly above the trap.

 

[CT18]

What your describing is not allowed in my area. A few photos might help. The washer hose should drain into a stand pipe with a trap on it or into the sink not connect to the sinks trap below.

 

[Ken New]

 

[CT18]

That is not legal in my area and i would doubt it is in yours.. Can you not drain the washer into the laundry tub.

 

[Ken New]

I dont see the problem. Its been like that for the last 24 years. What are you suggesting.

 

[CT18]

I am suggesting it is not piped to code. Look into washer stand pipes and i am sure you will get images on how your washer discharge should be. It should go into its own 2" line not receiving discharge from another fixture. If there is no vent on that sink then it is quite possible that the trap seal is being siphoned dry by the washer discharge.