I have 3 toilets. In one of the toilets I have large pieces of dirt and a layer of sand flowing into the toilet tank over the past year. The dirt actually makes its way into the toilet bowl.
Plumbers are puzzled about what could cause this. We have cleaned the tank but the dirt reappears.

The toilet was installed 15 years ago. The house is 75 years old. The toilet is a low flow Porcher toilet.

I would appreciate any ideas anyone has.

Joan Little