Question: There’s a black ring around the base of my toilet. What causes a black ring around a toilet base?
Answer: If you are starting to notice a black ring around the base of a toilet under the linoleum, you probably have a leak coming from the wax ring that seals the toilet to the floor. The color comes from a black mold or wastewater bacterium.
What You Can Do
To fix this issue you have to detach the toilet from the floor and replace the wax ring gasket with a new one. We would also recommend that the drip line under the bathroom be cleaned – as soon as you've got it off the ground. If your toilet is not flushing properly, the water gets backed up applying pressure to the wax ring causing a leak. If you’re not used to such work, save yourself the trouble and call a plumber to get done right the first time.