'13 Montana with Thetford Style II toilet. Sometimes when flushing, black particles are present in the flush water. The toilet has flooded the rig three times when the flush valve didn't close. I replaced the valve but it still did it. Since new, I have replaced the entire base (lever fell off), the valve and the ball seal. I'm replacing the toilet but would like to know what the black particle are.
PS...the particles are in the fresh water
