I have researched drowning fleas. There is a lot of good data at Can dish soap really be used to kill ticks and fleas? the summary there suggests if you wash fleas away in the yard, your pet well get them back tomorrow. But if you wash them down the drain they are gone forever.

There are multiple online reports of "drowning fleas" and killing them with soapy water. After looking for the science there does not seem to be much support for these fatal claims. There is little doubt that giving your pet a soapy bath in the tub will help remove the fleas, they may even appear dead. But in all likelihood these fleas are just waiting to dry out and be revived, hopefully in the city sewer. If you bath your pet in the yard, and than let the dry pet in the yard again the next day the clean pet and clean revived fleas will likely reunite. Soapy water is more likely to facilitate removal of the comatose flea from the pet and carry it down the drain. So it is reasonable to have noticeable decrease in the flea population after a bath. But excessive bathing has it's own risks and given the life cycle of a flea soapy baths alone are unlikely to be a final solution.

I believe some insects, like spiders if flushed or washed down the drain will often climb back up into the home.

Does the same hold true for fleas? Does flushed = "Gone" or "On a short trip, be right back"?

  • You can always make sure they're dead, and as you groom your pet after a bath, press these fleas between your nails(I've seen that regular shampoo makes them lethargic) and then just toss them in a container with a weak mixture of water and bleach, then pour that mixture down the drain.
    – Just Do It
    Commented Jun 18, 2016 at 14:25
  • Just a comment: If you need to give a cat a flea shampooing, the best approach I've found is in the tub, with a handheld spray head at low pressure and warm water, so the cat is never immersed but just being subjected to a heavy but warm rainfall. Admittedly my experience was with a very patient and trusting Siamese so other cats may object more even with this gentler approach.
    – keshlam
    Commented Mar 11 at 4:44

3 Answers 3


In the US, modern plumbing has a trap. A small amount of water stays in the trap to prevent sewer gases from entering the building.

If a flea is washed down the drain but doesn't get pushed all of the way into the sewer, it will hang out in this water pool, and thus, will never get dried out to revive.

Sometimes the traps of infrequently used drains will dry out, but the flea will die in 24 hours of submersion. The trap will not dry out in 24 hours.

  • 1
    @James Jenkins, I think zaralynda has it covered. I just wanted to add that the soap itself probably doesn't kill the insects unless it's an insecticidal pet soap, which I would use if I suspected my pets had them. What the soap does is break the surface tension of the water, so that instead of sitting on top of it and eventually working their way to the edge and climbing out, they sink and drown.
    – Dalton
    Commented Jun 20, 2016 at 13:18

Yes!!! I just tackled a flea problem in my house and while I was dealing with the problem I kept pulling fleas off my socks and washing them down my bathroom sink drain. A few times I noticed a flea or two hanging out in my sink so I thought maybe they weren’t going down the drain, so I stayed and watched them to make sure. A while later, there was a flea in that sink again. I started thinking maybe the water was attracting them to the bathroom sink. But then I wondered if they were somehow hopping out and that’s how I got here. Now that I think about it, I know this drain has a partial clog because my sink empties slowly and belches up a bubble before fully emptying. I bet they’re getting caught in whatever nasty debris is hanging out in the drain. They dry out and revive when the water stops and hop back out a little stunned but no worse for wear. They can probably even hold onto the sides if they’re coated with enough gunk. I’m guessing that running scalding hot water for a few minutes ought to do the trick. They are determined survivors. I give them that.


I believe you because the same thing is happening to me. Even when I run scalding water down the drain I'll come back later and find soft white unfed fleas in the bottom of the sink and in the tub also.Rex

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