So, I know I'm likely going to need to get a pro in for this. But here's my issue, and hope maybe someone has some insight in the meantime. My upstairs toilet flushes great, bathroom sink & bathtub drain fine, kitchen sink drains like normal. However, I just noticed a couple days ago that the basement sink is backing up whenever the upstairs toilet flushes.

A plumber friend brought his 100-ft heavy-duty snake over to spot the apparent clog in the main sewer line. He ran the snake from the basement all the way out to the trap at the curb. After multiple tries from both ends, he finds... nothing? So how is it possible for the backup to happen whenever the toilet flushes, if there's not a blockage somewhere, causing part of the flushing runoff to detour into the bathroom sink? Thoughts anyone?

Thanks in advance!

It could be a partial blockage where the snake will bypass the obstical and leave it continuing to partially block.

srloren

Would a partial block causes the basement sink to back up? Also, I should add he went out to the trap outside the home and had me flush several times, to see if he could water flow reaching the trap. Says he sees almost no movement. Just strikes me as odd that he'd see no passage to the trap, yet the 100 ft snake finds nada. The distance through my pipe to the trap is 27 feet. His snake is 100.

he is using the wrong head on the snake

he is 'probably' using a small spade tip (or none at all)

he 'should' be using a 'cutting type' head



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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Thanks for sharing that. So the basement was originally draining slowly at least, if I worked to plunge (after it gets backed up after toilet flushes). However, today, the basement sink wasn't draining even after plunging.

I used Drano Max Gel Clog Remover a few hours ago, in hopes that will help (I have to wait another 2 days before my plumbing service can come out & I don't want that basement sink overflowing with half-sewery water until then). The Gel did create a foam over the drain but otherwise it's still standing.

Only problem is, once the toilet flushes next, that basement sink will back up more. And this time, I guess I can't plunge due to the Drano. But I also cannot run the risk of the sink overflowing with icky water in the basement. I'd been able to manage it before today.