To start this post, I can flush my toilet 100 times and it functions perfectly. The only time it leaks is when the washing machine is draining at the end of its cycle. I have had 3 plumbers come out and look. We have replaced the wax ring multiple times, even installing a double ring. The flange is also in good shape. One plumber ran a camera into the sewer line and it was clear. I even snaked the vent pipe and checked the P trap of the washing machine, and both were clear. The washing machine is only 4 ft away from the toilet. I am at a loss right now and don’t know what to try next.

As a background, when this first happened, I replaced the wax ring myself. Then it happened again that night so the next day I bought a new toilet hoping it was just a hairline crack in the base. Sadly, that wasn’t the case. When the valve is off to the toilet and we run the washing machine, it doesn't leak and the valve isn't leaking either. Has anyone ever experienced this before?



Edited 1 times.

bad wax seal

the back of the flange MUST be on top of the finished floor
so that the toilet 'horn' sits INSIDE allowing proper space for the wax to seal



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

did anyone, while they had the toilet removed, run the washing machine?

sounds like partially clogged line, pretty standard for old cast iron pipes, I flushed mine out with buckets of hot soapy water in the toilet and had the washer drain into it's own pipe not the sink to flush it out when ever I do a load of wash. Wax rings just cant hold pressure so if the pipe fills up you will have a leak there and possibly gurgling at sink drain.