I'm adding a sink to what will be a new bathroom. The owner poured a concrete slab already but with no discharge for the sink drain. However a 2" dicharge line is provided opposite the wall where the sink will be, which is good. But the line is being used as the open discharge for the clothes washer. I'm afraid if the plumbing is slow or the machine discharge fast the sink may back up. The discharge opening is at 4 feet. Can I, should I, am I OK with code to do this? What should I do that's best. If there is some back up is there a check flapper valve I can place on the sink discharge pipe ? Michael

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Originally Posted by handymanmike

I'm adding a sink to what will be a new bathroom. The owner poured a concrete slab already but with no discharge for the sink drain. However a 2" dicharge line is provided opposite the wall where the sink will be, which is good. But the line is being used as the open discharge for the clothes washer. I'm afraid if the plumbing is slow or the machine discharge fast the sink may back up. The discharge opening is at 4 feet. Can I, should I, am I ok with code to do this? What should I do that's best. If there is some back up is there a check flapper valve I can place on the sink discharge pipe ? Michael

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Hey Mike,

If what you're proposing is to drain the lavatory into the washer standpipe that's not a real great idea. First because of your concerns about a back up and second because you would be double trapping the lavatory discharge, which is against code, and using the washer stand pipe as a local vent which is also against code. Is there another way? Regards, Tom