Sand Filter High PSI question

[mikemedic]

I have a Hayward High Rate Sand Filter. Lately when I backwash it the pressure goes down to 14 but within a few days it back to 20. I backwash for a few minutes and then rinse for a minute like always. All my readings are ok and the water is crystal clear. Any ideas? At the beginning of the year when the pool was green it was at about 11 PSI and then maybe creep to 16 or so and I would backwash. But this is how it is acting now and the water is clear. Any help would be appreciated

 

[JasonLion]

You might have some kind of blockage in the return pipes (normally very rare) or you might have turned off a return valve that you had open before.