My pressure has been around 28-30lbs for the last week or so. I backwashed today to get it back down around 20 psi. Soonafter i did it was back up to 28. is opening the filter and washing the fins inside the filter normal maintenance? How often? How do you clean it? if i open the filter will i have to shut off a valve? The top of my filter is above the pool water level. Thx.