Yes, CLR PRO Septic Treatment can be used in an RV or motor bus.

The Tarn-X was probably left on too long, was not rinsed properly, and/or allowed to dry.

Pour enough Calcium, Lime and Rust Remover to cover bottom. Swish around in pot or pan. Add one cup of warm water, allow mixture to soak for two minutes and thoroughly rinse with cold, clean water. Using a soft scouring pad while our product is sitting on the stains is recommended. Always check with the manufacturer of your coffee pots, pans and tea kettles first for their recommendations of products that are safe and effective on their materials.