They finally finished my pool which has solar heating installed. During the indoctrination, the pool company told me about backwashing the filter and adding new DE when ever the gauge on the filter went to the "dirty" setting. Seems easy enough, but I'm a little confused because of the pressure changes when the solar system is being used.
At night or in the early morning, the temperature is not high enough, it the bypasses the solar system. When this happens the pressure at the filter is around 19 psi (the very low end of the "Clean" setting). When the sun comes up and the roof heats up, the solar system kicks in and the water is piped up to the roof and back to the pool. This obviously causes the pressure at the filter to increase. When the solar is working, the pressure is around 26 psi (near the high end of the "Clean" setting and close to breaking into "Dirty" territory).
So my questions are:
1). Should I not backwash the filter until the pressure reaches the "Dirty" limit when the solar system is not running? In other words, only read the pressure with pool-only circulation, not circulation through the solar system?
2). If the gauge reads say 26 psi without the solar system being active (close to the "Dirty" pressure) and it jumps 7 psi to 33 psi when the solar is active (beyond the "Dirty" limit) will the increased pressure hurt the pump or filter or anything else?