Soaked cat litter box containing some hardened litter on bottom in sink and spilled it in sink and went down sink. How much litter will cause clog?

  • Type of litter might make a difference, clumping/plain, loose/solid. Sink drain pipes are at least 1.5 inches in diameter, so hopefully you flushed with enough water. A big handful might cause problems.
    – crip659
    Jan 8, 2023 at 17:00

2 Answers 2


How much is required to clog it not really the right question. The real question is how to clean it out as best as possible.

Most of it is almost certainly sitting in the trap below the sink and the trap should be removed and emptied; after the trap has been cleaned, run water for several minutes to try and wash away anything missed. Anything that made it past the trap will likely flow all the way out of your plumbing into your septic or the sewer depending on where you live.


Most cat litter is essentially clay. The risk is that it might settle at a low point in the pipe. Small amounts will be washed downstream, otherwise washing your hands after gardening would be a problem. Larger and/or more frequent amounts may build up.

One place where this is most likely to become a problem is the sink's P-trap, so looking at that you can get an idea of how much it would take to restrict flow. If the P-trap has a drain plug you could drain it and remove any such accumulation; if it doesn't, just running a substantial amount of water through the sink (a few cycles of filling it and draining it) will probably be sufficient to flush most of it into the drain.

If you do see evidence of clogging, the standard tools (plunger and snake, not chemicals!) should be able to shake it free. I have a small plunger I keep around for sinks to avoid the ick factor of grabbing a toilet plunger for the purpose.

But in general, just rinsing the remaining residue out of an emptied and scraped cat box shouldn't be a problem. I prefer to pour down the toilet, but if a tablespoonful or three goes down my drain I really don't worry about it.

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