Intermittent cutting out of the pump
The HLP pumps are fitted with hydrostatic bearings as described above which must be filled with water. if air gets into the bearing section then the pump will start to run hot and the thermo switch will cut off the pump until it cools down again - a safety feature to stop you burning out the pump.
If this happens then the air must be bled from the pump - see section on bleeding.
Pump fails to start
From time to time you may find that your HLP pumps refuses to start.
The most likely cause for this is calcium build up or a snail jamming the�impellor - See the article on cleaning.