tado thermostat: Legionnaires’ disease protection symbol
The boiler is firing to disinfect the hot water (Legionnaires’ disease protection).
Applies to: tado° Smart Thermostat controlling hot water. What you see: a symbol.
What to do
tado° Help Center gives no step for this on the page cited; the meaning above is all it says.
tado ties this to the boiler or heating system. What the symbols on a boiler’s own panel mean is on the boiler symbols page.
Source
tado’s own help page, read on the date shown.
- tado° Help Center: What do the symbols on the Smart Thermostat or Wireless Temperature Sensor user interface mean? — tado° Smart Thermostat and Wireless Temperature Sensor (V3+ and earlier). support.tado.com Checked 2026-09-29.