I've got a Hayward S180T sand filter (150lbs according to the manual) and a Hayward PowerFlo Matrix 1.5HP pump. I've never touched the sand except for deep cleaning with a hose. I'm wondering if I've lost some over the last 2 years due to backwashing and need to add some more. Problem is, there's no fill line. I'd like to avoid taking it all out just to weigh it and put it back in.
If I top it off, what's the risk that I overfill the sand? How would I know I put too much in? Can you put too much in?