Has anyone been installing tile lately?
Sounds like tile grout.
Got frustrated with a constantly clogging toilet recently and pulled it to see what was going on. Much to my surprise I discovered a thick, sandy buildup running down the inside of the drain pipe, starting where the toilet flange was. It was grey and relatively odorless (fortunately for me) and it crumbled apart fairly easily when i tried to remove it with a putty knife. Downstream about a foot or so the pipe seemed clean and free.
I scraped as much of it out as I could, but some escaped down the tube to (hopefully) wash out. The blockage was thick enough at the top to be causing my flushing woes. There was no blockage in the toilet itself and the stuff had clearly accumulated over time - it was nicely sculpted by the water flow.
I don't have hard water problems at all - so what was/is that stuff? Should I proactively start pulling and inspecting the other drains? Should I chase the gunk with a CLR-like drain cleaner? I've pulled weird stuff out of drain lines before, but this one had me scratching my head.
Nope - no tile anywhere around. It had the look of something deposited over time though - you could see what looked like layers in it.
Drywall mud could do it as well...
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013