I've been fighting a swamp and every time I run the filter the pressure rises within 1/2 an hour or so and needs a backwash. I recently purchased the home so do not know the back story of the the filter. However, I did inspect the filter and the grids though off white, they were not caked or covered with DE. I ran the filter through a few more cycles of backwashing and adding DE. When i opened it again there was not much DE laying around so i just hosed off all the grids in the filter body. Obviously with filthy water the filter will need a lot of backwashing and recharging, I'm just not seeing any increase in time until the pressure rises.
Anyway, the 1st few times I backwashed the water was anywhere from black to greenish. I figured tons of dirt and dead algae were entering the system so I added stockings to the skimmer basket in order the catch some of the larger stuff. The skimmers indeed fill up very quickly with what looks to be green dead algae. However, the filter pressure still seems to rise within 1/2 an hour or so and now while back-washing the sight glass is only a milky white color. I'm aware that the dead algae is must often white/gray so is this a normal color or should I be. Also not that the pool is still has horrible visibility and is a lighter green.
When freshly loaded with DE the pressure is 14-15. The filter is a on old Metal Nautilus 36Sqft and may well be about 40 years old. Like mentioned above the grids and a brownish color, but other than that are in good condition, no tears or rips I can detect. Does this all sound normal or should I give the girds a nice soak in dishwasher powder. This area has always had public water so I don't think an acid soak is needed. Of course there is always the chance that the previous owner acid soaked the grids and hardened all the old biological matter on the grids.