[Slash]

I've recently purchased a 500 litre system  but found the water stopped pumping.
When I looked into the tank there was about 100 litres left  in the tank.
Is the water  inlet to the pump 4 to 5 inches above the base of the tank as I can't see the pump hose where it feeds from

[Splash & dash]

Ime guessing if you find the outlet from the tank on the outside then you will be able to measure that and determine how low down or high up in the tank it is .