hi, we have a low level water tank at ground floor level and another high water tank 7 meters above the ground.

We want to pump water from the low level tank into the high level tank.

Any ideas how i work out what pump duty i need. thnx

You should be able to lift the water with a 200 or 300 series Mitsubishi or a Hitachi. There are stronger pumps you can get-Grundafos, but if you are just pumping one tank up to the other you should be fine. If your well is lower than ground level you would be close to the end of what can be lifted upwards.