A serious company built the pool and installed the machinery. Also, I haven't had any problems for the last 12 years so probably the amount of sand was ok. This guy just stuck his hand in and said it was low. I estimate it was a little over half full. He then went on to tell me that the sand dissolves with time, which it seems is untrue.
Never heard that one before. I didn't know all these years I could have been topping off the sand filters instead of changing the sand out. Don't let him add more sand unless you have him change the old sand out first. Mixing a few bags of new sand with the old sand isn't going to improve anything.
Also the sand will feel loose and free in the middle. Down along the inside walls all the way to the bottom is where the real gunk collects.
Those Tr 100 sand filters are 600lbs. 600lbs of sand takes you to the top line just at the diffuser pipe. Thats where everyone I know fill them to. Thanks for posting those charts.
Thanks for the very clear indication. That is about where he reached his hand to when he opened it, so I think the sand is fine. He also took out a handfull and it wasn't clumped or hardened. It looked fine although there were different sizes mixed together.