Polystyrene Insulation Inside a Toilet Cistern Tank

No: do not spray expanding foam inside a toilet cistern tank; use a purpose-made interior tank-insulation liner instead, or fix a leak, running toilet, or high bathroom humidity first. The polystyrene or “Styrofoam” found inside some tanks is usually a factory-fitted insulation liner designed to reduce condensation on the outside of the porcelain. This guide…