Immersion heaters have titanium sheaths
Titanium Products now offers the Backersafe range of titanium-sheathed immersion heaters for domestic-hot-water systems in areas with hard or aggressive water. The design of these immersion heaters isolates them from the electricity supply if the primary thermostat fails with the contacts closed, eliminating the risk of boiling water.
This protection is achieved by a resettable thermostat in series with the primary thermostat. If the primary thermostat fails, a low-cost replacement can be fitted and the projected thermostat reset.