Common, but not normal. It's grease. Sort of like clogging of the arteries for your drain, which slows down the water and makes it clog again that much faster. Aside from scraping it out with a paint stick (that's what i do), it would proably be helpful to run plenty of hot water, followed by draining a basin full of hot water soapy Ajax water. Maybe a foaming drain cleaner would help, too, though one shouldn't get in the habit of using drain cleaners too often.

Thanks for the reply. I'm sort of wondering how far down in the 'system' that stuff goes. Don't guess there's a whole lot I can do about it short of what you suggest.

Thanks again.

Grease down the drain is bad for your plumbing, bad for septic tanks, and bad for municipal sewage treatment plants.

It may not run that far...the pipes under the sink -- particularly the P-trap -- are where most of this stuff settles. However, you may need to re-consider what goes down the sink. Does anyone routinely pour grease of any kind down the drain while cooking, rather than disposing of it in the garbage. Do you have a garbage disposal, and if so are you putting anything in it that could cause grease buildup in the pipes?

I remember watching a TOH episode where the homeowner was adding a basement toilet. They needed to attach to a drain that came from the kitchen above. When they cut the pipe, it was filled with the same crap, nearly completely blocked. This was about 10 feet from where the pipe went up into the kitchen. They stated afterwards that they went in and snaked the drain line for the homeowner to clean that crap out.

Greasy foods leads to greasy drains. Biofilm or not, bad habits of using the garbage disposer for those greasy foods, etc. lead to the same result. (And I'll bet it does have a healthy composition of grease.)

I know these are older posts, but this has happened to us twice now. We live in the bottom unit of a building with 2 units above us. We were told that it is occurring in the units above and causing our unit toilet to clog and back up into the tub. I’m sick of this! The plumber has to come in and use an industrial sized snake to unclog it. The plumber says it’s because we are the bottom unit(gravity.) Then this greasy thick brown stuff gets on our bathroom things. Is this biofilm toxic? I’m worried.

We had basically what looks like white yogurt that was almost filling our shower drain. I tried all of the commercial drain openers to no avail, including the slow-drain enzyme cleaners. Of course, I also tried vinegar, bleach, ammonia, and so on. (By the way... don't ever believe that combining vinegar and baking soda is a remedy to anything. It's a fun chemical reaction and seems like it's doing a crazy good job but what it's actually doing is nothing. Soda neutralized vinegar and basically turns it to water. So it's pointless.)

Anyway, I had the same fear as many others have posted about what the rest of the pipes must contain.

So I search around and found a couple references to the bio-slime, most of which didn't include a white version, but they seemed to be the closest resemblance to my drain problem. All of them talked about bacteria and fungus.

You know what kills bacteria and fungus? Vitamin C. Yep. Otherwise known as ascorbic acid, you can buy it in powdered form and in various volumes. I thought it was worth a try so I ordered a 5 lb. bag for 30 bucks. You may be able to find it cheaper if you can find a non-consumable one somewhere.

The process I tried was to wait until the water had drained after a shower and apply just enough to cover the white slimy stuff I could see and just let it sit there until the next shower. When I looked at it the next morning, I was happy to see that (even though it looked awful) the white stuff was turning yellow and drying out. So apparently this was killing it. I kept that process up for 4 more days. Toward the end of those days, I was adding a just a small amount of water so it would carry the powder down into the pipes.

End result: It worked! I no longer have the white slime build-up. I only used about half of the 3 lb. bag so I'm ready if the blob attacks again!

That’s a great idea! Thanks

It's biofilm like Paul 2015 said. I just took my pvc drain cap off to pull out an old rusted screw and my cap and drain was full of it. I assure you that no grease is being poured in my upstairs drains!

We live in an apartment on the 9th floor and our toilets are slow flushing.

We noticed our main toilet was clogged so we bought a snake and YouTubed how to snake it.

All of a sudden out came this thick black jelly like substance that was entangled in the tip of the snake and smelled like sewer.

We did it a couple more times until there was no more black stuff and it flushes perfectly now

I'm assuming it was biofilm?!? 🤷