Situation and problem

My buddy has a woodworking shop which he graciously allowed me to use for a woodworking project. I am a total novice in these kinds of areas, which will be doubly clear in a moment.

After applying the last coat of polyurethane to the project, I had about 2 tablespoons of polyurethane left over in my cup I was pouring out of.

Being very unwise and uneducated, I poured about 2 tablespoons of polyurethane down the shop sink. (For those on metric, Google tells me 2 tablespoons is roughly 30 milliliters.)

Now the sink drains very slowly. I'm assuming this is because the poly solidified in the pipes and created a partially obstructed drain. That's just my newbie guess, maybe some different interaction happened.

Additional details

I did an internet search before the cleanup stage to see what dissolves polyurethane. So I mixed the poly with some paint thinner before pouring it down the sink. (Later, I learned neither poly nor paint thinner should be poured down a sink.) In any case, it didn't seem to make a difference related to the blockage, as the sink still ended up draining very slow.

My buddy knows about all this. I'm just trying to get additional info so I can get this fixed for him and correct my mistake.

My buddy says that the water from his shop doesn't go directly to a city waistline. It goes to a sewage ejector pump that's in the shed outside. And this sewage ejector pump doesn't operate all the time.

One thing I've researched, but haven't tried yet, is using vinegar to dissolve any polyurethane blockage. It's safe to pour down drains, and supposedly vinegar dissolves poly. Though it might take a large volume or be a very slow unblocking process?

Help appreciated!

Any insight into how I should proceed would be much, much appreciated. I certainly don't want to make things worse as I try to make them better.

  • How good of a buddy is your buddy ?
    – Traveler
    Jun 14, 2022 at 22:50
  • 2
    If you are lucky it is still in the P-trap, so take it out to check
    – Traveler
    Jun 14, 2022 at 22:51
  • What are the pipes made out of? Two tablespoons not that much, would try using a snake.
    – crip659
    Jun 14, 2022 at 22:52
  • He is a very good friend of many years. I can check the P-trap. I'm curious what the "worst case scenario" is and what's the "best case scenario" here.
    – DCO
    Jun 14, 2022 at 22:52
  • 1
    Snake would not be strong enough, but will locate the problem. Think there might have been a partial clog in the pipes before that the polyurethane made worst. Expect to replace the piece of plumbing where the clog is. P-trap is a good guess, but a snake should locate the piece/section of pipe, and can have the piece handy to replace when taken it apart.
    – crip659
    Jun 14, 2022 at 23:03

1 Answer 1


Start with (no, wait - buying your buddy a large quantity of the GOOD version [in your buddy's opinion] of something they like a lot, then...) removing the trap, assuming the trap is not one that has to be sawn out to be removed (I hate those, and I hate the people that put those in anywhere but underneath a concrete slab.) A nice normal trap is unscrew 2-3 slip joints with a bucket to catch the slop and get right to the guts.

At that point you may well find your major blockage, and be able to either remove it, or simply replace the whole trap if it's stuck to the trap very badly. If you need to snake, better to start with the trap removed if possible, it takes one set of turns out of the start of the run.

Alternatively, just call in a plumber...

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