Part of my problem is not knowing the names of what I'm referring to, so feel free to suggest title edits please.

A bathroom sink is draining very slowly after someone bearded shaved, despite them gathering most of the hair out of the sink. I expected some hair to be clogging the J-trap, but when I went to clean that out, I found there is no J-trap and instead the sink drains into the lower end of a cylinder, with the cylinders outflow on the top. Pictures below. It looks like a garbage disposal to me, but that doesn't make sense because this cylinder is not directly connected under the sink and also it is not powered.

I think the cylinder might have the same purpose as a J-trap, given water enters it low and has to rise up high to drain out. That would mean there is (always?) standing water in the sink's drain pipe, at the same height as the cylinder's outflow pipe, because how else would water leave this cylinder.

My question is: what is this cylinder, and how to I clean it out like a P or J trap? I thought to unscrew the base of it since it has the square bottom to grip and turn, then catch what drains out and use a stick to poke out remaining gunk. Figured I'd ask here first, and may also try plunging or poking around the sink drain itself first to see if that solves the problem. Thanks.

unique trap under sink

unique trap under sink 2

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    BTW- What you would have there, if it were not for the drum, would be an S-trap. A P-trap would exit the back of the cabinet and into the wall. While I suppose J-trap does get the idea across, it's not a common term that I'm familiar with. Of course, I'd never seen nor heard of a drum trap, either, so what do I know... – FreeMan Mar 3 at 16:17
  • Depending on pipe size, (the downward drain pipe does seem to be bigger than the sink tailpiece, which is good for this) it might fit the "one-pipe" setup which "looks like an S-trap but actually isn't" (the bigger drain pipe supposedly can't get full enough to siphon) but my local code forbids that part of IPC anyway. – Ecnerwal Mar 3 at 16:21

That is a drum trap. [Evidently also called a bottle trap in some parts of the world, per comments] They are rather old school, and out of favor in code now.

I'm more used to finding them embedded in a floor with the clean-out on top (for a tub application) but yours does seem to have the cleanout down.

Fair warning - they seem to be above average at "wicked gross" - since it's slow, not stopped, I'd run some bleach solution through (1 cup to a gallon) wait a while (if not urgent, overnight - if urgent, 15 minutes or so) then run a couple of gallons of clear water to rinse out the bleach, then put a big catch basin under it and put on gloves before opening it up.

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    Just curious.. how'd you find out about "wicked gross"? Hopefully, not the way I did. lol :-) – JACK Mar 3 at 17:26
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    Probably all too similarly, @JACK – Ecnerwal Mar 3 at 17:31
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    Whatever else you do, don't make the classic mistake: Turn the taps full on, preparing to flush all the crud away down the sink, BEFORE you replace the trap. Everybody does it once in their life.... – alephzero Mar 4 at 2:41
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    My fun was a few years ago when the drain from the sinks (two sinks in kitchen) got so clogged that if you ran the disposal on one, it would output into the other sink, dishwashers overlowed into sinks, etc. I opened up the vertical pipe in the basement leading from the kitchen...and got old chicken soup (and probably some other stuff) all over myself. You don't forget these things too quickly...and you don't make the same mistakes twice! – manassehkatz-Moving 2 Codidact Mar 4 at 3:21
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    In my experience that is a BOTTLE TRAP. – Mike Brockington Mar 4 at 8:45

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