We recently had an issue with a leaking toilet in our 1st floor powder room - which was not discovered until it was way too late. After removing the toilet, I discovered water damage to the vanity, drywall, floors, etc. Our simple toilet repair is now a full-blown renovation... but we are waiting for our insurance adjuster to inspect the damage before we can proceed with the repairs. I have removed everything from the powder room, and the supply lines and drain pipes are exposed.

Here's the problem... when the upstairs toilet is flushed, we get about 8 oz of waste water pouring from the exposed sink drain pipe in the 1st floor powder room.

Is this normal?

Can I stop it from happening since I cannot make repairs until our insurance people get their act together (I currently have the drain pipe stuffed with a rag)?

Thanks!

Here's the problem... when the upstairs toilet is flushed, we get about 8 oz of waste water pouring from the exposed sink drain pipe in the 1st floor powder room. Is this normal?
No it's not!

Can I stop it from happening Sure sounds like a partial clog downstream from the vanity. The solution would be to snake from the vanity roof vent. Put out enough snake to reach the base and 16 feet more. Good luck, Tom