Harvia Water Heater WP250TH For Harvia ThermioHarvia Water Heater WP250TH For Harvia Thermio The stylish steel outer shell of the Thermio water heater suits any sauna. The Thermio water heater heats the water quickly, as the smoke pipe acts as a wall in the water tank. The tap solution is placed away from the hot water tank and the stove. The tap can be installed in three different ways onto the benches or the wall. This makes the tap safer to use, as there is no fear of hot water splashes.