Add more sand?

[MandaPadanda]

So I just did a deep cleaning of my sand (for the first time) yesterday....omg it was gross, and I quit after an hour. I plan on doing it again this weekend.
Anywho, when I opened the sand filter I noticed that the sand is WELL below the "minimum" line on the standpipe (i think that's what it is called). I know I put the proper amount in when we first set the pool up. Is this just due to settling and not an issue or do I need to add more sand? We have not lost any sand.

Thanks in advance!!

 

[woodyp]

For whatever reason it seems to be gone....I'd add sand up to that line. On most filters this translates to about 2/3 full of the filter body. The rest empty space is called "freeboard".