If there is air in the system, the pump won't work, and running dry is not good for the pump. There are pumps specially made for this problems, and can run dry to, but they cost some money:

http://www.moespompen.nl/p/fti/centrifugaa...pen/11/SP+Serie

Best thing to do ís to make sure there is nothing in the "suction" line from the tank to the pump, and the water in the tank can reach the pump. More water in the tank is more pressure on the pipe lines. Best to install a minium water level meter in the tank, then the water inlet feed for the tank will automatic go on, and shut off when full. So 2 meters on the tank.

Is there any chance that you are pumping the tank dry or to a low level that is allowing air into the pump inlet , if yes - you need a low level cut-out wired into the pump power supply.

Is there any chance that you are pumping the tank dry or to a low level that is allowing air into the pump inlet , if yes - you need a low level cut-out wired into the pump power supply.

Indeed, I think this is the problem, the tank water level, needs to be kept at a minium for the pump to substain under water pressure. If air comes in, it's over, and you can start from the beginning.

In my case the pressure switch area was free of insects BUT you have made an excellent point ans insects and ants get everywhere here in Thailand. I will bear your comment in mind when/if other item accessible to insects become unreliable.

I have had ants build nests in my unused espresso machine as well as in my water boiler, both times it's been the small black ones (that apparently aren't edible according to the family ). They seem to love living in electric appliances.

Thank you for an interesting thread. My pump has exhibited similar symptoms to those described here and I have learned some new things by reading all the helpful suggestions. Good job guys.

Agreed - a very interesting thread. I too have learnt a lot and will check the problem I have with my Mitsubishi pump which vibrates/ jumps when it shuts off. One question that was not answered though - are the Hitachi pumps 'better' than the Mitsubishi pumps in general. I have a Hitachi pump that pumps water for the garden trees and grass etc... I actually 'forgot' its there as its worked for 6 years with NO problems at all. So maybe I will swap that with the Mitsubishi pump that currently 'control' the house water!!!!Maybe not - I would buy a new Hitachi pump - best not to change a set up that works - otherwise the grass would probably die knowing my luck!!!