I noticed a few days ago that, whenever my dishwasher is draining, the sink in my kitchen island gurgles (glug, glug, glug). I THINK that the sink connects to the main kitchen sink drain underneath the floor. Any idea what could be causing this? Also, I'm not sure if it's related but I just noticed that my upstairs bathtub is draining really slowly now. But I'm pretty sure it's a separate line until it gets to the Septic connection like everything else.

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  • 3
    Sounds like a blocked vent somewhere. Is the island sink noise a new development? – isherwood Oct 22 '18 at 13:42
  • I'm curious as to why your dishwasher isn't draining thru the garbage disposal depicted in your diagram... Not allot of details to go on here but an educated guess would be a partial blockage in the drain system itself and/or improper or partially blocked venting. – BillWeckel Oct 22 '18 at 13:44
  • @isherwood the sink gurgling is a new development. – Programmer Oct 22 '18 at 13:45
  • @BillWeckel This is how it was set up when we bought the house. – Programmer Oct 22 '18 at 13:47

There's a blockage in the venting where the island ties-in. The 2 locations are commonly vented together, due to that loop under the island sink. A T-fitting instead of a Wye may have been used to tie-in the island and this is why only a Wye or directional fitting should only ever be used.


I think it's because your sink drain and your dishwasher drain are somewhere connected. It's the same in mine.

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