I know it's recommended to backwash a filter when the pressure rises a certain psi above the psi when the filter is clean - the psi rise caused by dirt/debris in the sand interfering the flow.
However, my pressure hasn't risen in the two months since I've opened the pool. (I don't have an extremely dirty pool (no leaves, twigs etc., just some dirt/dust/pollen and the usual dead bugs/worms).
Should I just forget about backwashing until the end of the season, or should I backwash after a certain amount of time 'just because'? I recall reading somewhere that the effectiveness of a sand filter actually increases as it gets dirtier (I guess up until there's too much dirt for proper flow).