Safety: Short cycling can reduce component life but is not usually an immediate hazard.

Increase flow: Open the hot tap more to maintain a steady flow above the heater's minimum.
Avoid rapid on/off: Do not repeatedly open and close the tap quickly.
Check mixer valves: If using a thermostatic mixer, test with a standard mixer to see if behavior improves.
Service adjustment: A Termet technician can check minimum gas rate and modulation settings to reduce cycling where possible.

Water heater frequently turns on and off in short cycles when a small amount of hot water is used.

Possible Causes