I accidentally poured some mortar and grout down my bathroom drain when I was cleaning the remains of a bucket of mortar after tiling the kitchen. The drain was plugged up pretty bad so I tried to scrape some of it out with a wire hanger down the overflow, and that got it flowing again, but its still draining kind of slow.

It's an old house, so the drain isn't PVC, it's galvanized, or bronze, or whatever they used back in the 50's


You probably (and hopefully) have a large amount of sand/grout stuck in the P trap. If so your best bet would be to remove the P trap and give it a good thorough cleaning (out in the yard, with a hose).
(While the trap is off you'll be able to inspect the tailpiece and the drain line as it goes into the wall and clean those up too if necessary.)

If you can't detach your P trap you have a few options:

  • If your trap has a cleanout nut, open it up and run water through until gunk stops coming out (you can employ your wire hanger here too, to "encourage" it).
    (My experience is most older pipes that have such a cleanout nut are so old that the thing is frozen and can't be opened without breaking the pipe, so be careful if you try this)
  • Remove as much of the tailpiece as you can and clean out the trap with a shop-vac and/or spoon/wire/etc.
  • Work a snake down the drain and whip it around like crazy while running LOTS of water
    (In the hope that you'll wash enough of the grout further downstream that (a) your drain runs quickly again, and (b) it doesn't clog your pipes further down the line where you can't get at it.
    This is really a last resort and just delays (or moves) the need for a proper fix...)

The chemical I know for cleaning mortar is muriatic acid. You should be able to find it in a home improvement store. You might try pouring a cup or two down the drain and letting it sit for a few hours before hitting it with a plumbers snake and a lot of hot water. My only word of caution is that I don't know if it would react with the drain pipes at all, and it's probably not safe for a septic tank.

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    HCl is not super dangerous, but you can easily eat a hole in your drain, burn yourself, or cosmetically mess up other stuff in your bathroom. – dbracey Aug 21 '12 at 16:31
  • @dbracey, good point. Wear gloves, avoid the fumes, and be ready for a bigger repair. I've heard it being used to remove concrete from cars without any damage to the car body, but YMMV on a drain line. – BMitch Aug 21 '12 at 16:55
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    The acid may produce gas, so be prepared for sprayback, and DONT RINSE WITH HOT WATER - use cold, then hot after the acid has been rinsed away. Still, I'd just take the drain apart and skip the chemicals. – dbracey Aug 21 '12 at 17:13

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