Big hello to every one, new to this

tyrone65

Hi i have a 2019 Bailey Autograph 79-4i, the fresh water tank is reading 30%  when its full, so when its used its 30% it thinks its ety so pump cuts out, although it still has 70% of its water left.

I have been told that i need to re-calibrate the water sensor, but i dont know how, any ideas