5 PSI is over 11' of extra head which can significantly reduce flow rate in a pump no mater what filter type. For example, with your pump (Carl), if your normal operating point is 54 GPM @ 40' of head, at 50' of head, the flow rate would drop to 40 GPM going from 50' of head to 60' of drops it to 9 GPM! Personally, I would not let the filter pressure rise more than about 25% of the clean pressure to keep flow rates up. But then again, if that meant backwashing every week, I might stretch that.

Dansdad,

My size comment was regarding kelmvor's comments. But is sounds like you have fairly large filters.