I can't figure out why my kitchen sink drain keeps clogging. I've bought several bottles of Draino type stuff and they work for a day or two. But if I don't use my sink much in 2 or 3 days and then finally get around to hand washing my dishes (since I don't have a dishwasher) I find my sink won't drain again. Why is it clogging when it's not being used?

  • What type of dwelling? Single family home, apartment, high rise apartment? How long has this been happening? Also I highly recommend you don't use chemicals for unclogging sinks but instead use a hand auger. It's better for your pipes and the environment. Also if your trap can be easily removed, take if off and give it a good clean (just make sure you have a bucket under it when you take it off). When you take it off, you will also get an idea of what is clogging it.
    – diceless
    Commented Nov 18, 2014 at 19:25
  • It's a one story house built in early 70s. The sink has a built in metal cross at the drain hole that makes it impossible to get a snake through it. I doubt it's the trap. I believe something is growing in the pipes beyond the trap. But other than mold what could it be?
    – Lauren
    Commented Nov 18, 2014 at 21:17
  • How long does the sink run before it backs up? Can you run the water for a minute or does it back up right away?
    – diceless
    Commented Nov 19, 2014 at 1:11
  • It doesn't back up immediately. It takes a minute. Once after I used some draino product I noticed it seemed be better at first but then eventually water backed up to the sink again.
    – Lauren
    Commented Nov 19, 2014 at 5:23
  • You might want to get a plumber out to clear your line. Could be grease build up or even roots in your line. They will be able to tell you for sure and they will have to power auger to reach the trouble spot since it doesn't sound like it is next to the sink.
    – diceless
    Commented Nov 19, 2014 at 16:39

2 Answers 2


Although it's rare, it could be that the Kitchen Vent pipe is clogged, thus causing slow draingage, or now drainage. Could be that leaves have collected there, or bugs have built a next. Google "Kitchen Vent Pipe Clogged" and see if the articles there are helpful.

  • A symptom of this would be that it would drain alright with a bit of water (such as if the tap was running), but not if a large quantity of water was put down the drain at once (such as when draining the whole sink). This may help @Lauren diagnose the issue. (Also in addition to clogged vent, consider: improperly installed vent, or vented using a 'cheater valve' which is now malfunctioning)
    – gregmac
    Commented Nov 19, 2014 at 20:03

If I were to guess and this is just a guess. I would say you have cast iron drain. I would say that it is rusting on the inside and that the drain itself is just a microbe of the width it used to be.

Given that it is rusting on the inside, it will get a little prickly when dry. It will catch some food and grease and quickly clog. I have seen this happen in dozens of homes. I guess this because your house is at that magical 40+ years where almost all homes with cast iron start having issues.

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