Lehetséges ok(ok):

The nut has not been locked up.
The seal ring is damaged.
Too high water pressure.

Megoldás

Tighten up the screw.
Change the seal ring.
Reduce water pressure.

Lehetséges ok(ok):

Thermometer is damaged.
Furring in thermometer.

Megoldás

Change the thermometer.
Cleaning or change

Lehetséges ok(ok):

Valve fails.
Pipe clog.

Megoldás

Change valve.
Clean the pipeline. 

Lehetséges ok(ok):

Great abrasion on float.
Furring on float and plastic pipe. 

Megoldás

Change float.
Clean furring.