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I have washing machine down at the basement and pipe out the grey water with a pump over to the waste water drain. However, it appears that the water from kitchen sink just above the basement is shared the same path. So when my pump starts to pump water some of the water goes up the kitchen sink along with dirty stuff into the sink.

Should I put a check valve below the kitchen sink? would that help? or could I do to fix this issue?

The reverse is also an issue: it appears that water draining from the kitchen sink would go down to the drain, some water would always goes down to the pump which trigger the pump to come on and in turns pumps some water and junk back to kitchen sink.

I have actually since install a check valve in between the pump and the drain line. So at least now the water from kitchen sink would not overflow down to the pump which triggers it to pump back up again.

I also felt that there's a plumbing problem here. I'm not sure how to fix this. Drain seems to work because the water from washer would pump out eventually, some would always flow up to the kitchen sink along with junk, with the check valve installed now for the basement pump at least now the water from kitchen going down to the drain to basement would not overflow over to the pump now.

What would happen if I put a check valve also under the kitchen sink. So only allow water to go down? with the existing check valve between the pump and the drain (only flowing out to the drain), and now new check valve in kitchen sink that only flowing down to the drain. Would this work? that water would not back up the kitchen sink, and kitchen sink water would not back down to the pump in basement, eventually all the water would exit out of the drain properly. or would this create a problem?

I attached a picture of the setup. (The very thin blue arrow indicate the diretion of water flow for check valve) The red check valve is the one I am thinking about adding.

Thanks.

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  • Check valves on drain lines are not very common, and I'd worry about it getting clogged. It really just sounds like it's actually plumbed incorrectly, and that for likely comparable to what it would cost to add a check valve (backflow preventor) you could just change the way the pipes are run and avoid the issue. A picture and/or diagram of how things are connected would help a lot here. – gregmac Apr 25 '17 at 13:43
  • I'v already seen lots of check valves for this same issue and works wonder full with no issues of clogs Etc. Use the regular check valves tipicly used for sump pumps. Good luck – aofkj Apr 26 '17 at 4:24
  • What would happen if I put a check valve also under the kitchen sink. So only allow water to go down? with the existing check valve between the pump and the drain (only flowing out to the drain), and now new check valve in kitchen sink that only flowing down to the drain. Would this work? that water would not back up the kitchen sink, and kitchen sink water would not back down to the pump in basement, eventually all the water would exit out of the drain properly. or would this create a problem? – rvpals Apr 26 '17 at 17:25
  • @isherwood thanks for pointing that out. I was wondering how to get rid of that. Looks like it's ok now though. – rvpals Apr 26 '17 at 17:44
  • Yep. I edited them out for you. – isherwood Apr 26 '17 at 17:44

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