I asked this 2-3 years ago and got replies from helpful people but didn't get any helpful replies.
To recap regarding my setup.... used pool, bought from a 'pool guy' close to 5 years ago. The sand filter was painted with a textured paint and there's no labels left to view. It looks identical to a Pentair Sand Dollar filter. The label on the pump doesn't match anything anywhere. I posted pics of the pump and filter years ago along with the label and no one could determine what exactly it is that I have.
This is my first pool. And at the time of buying it and then given about 1 minute of instructions on how to backwash the filter, I didn't know what else to ask at the time. Nor did I think to ask for any details about the filter and pump. I can no longer get ahold of the 'pool guy'.
First 3 years, everything was great. Last season and even worse this season, the filter is just doing practically nothing... meaning not cleaning well. While vacuuming the bottom, the suction drops too low to 'suck' after about 5 minutes. I then backwash.... I can backwash for 30 seconds, or 5 minutes, and when done backwashing, I get about 5 minutes of suction until it stops again.
So... I take the head off the filter... first time ever... thus my question again (in a minute). I first though removed the drain plug. No water came out. After taking the head off, the filter was full of water. I got my shop vac and started vacuuming, with the hose about 6 inches in the filter. Only water is in the canister when I dump, not a single grain of sand. I do this again, and again and again (very small vac). I get about half the water out and I have the vacuum hose about 2 feet or more in the filter. Vac is full..... I dump it.... only water. Still not a grain of sand to be found anywhere. I keep doing this until I get about 3/4 of the filter empty before I start hitting sand.
So now, I have all the sand out. I have not purchased sand often but have somewhat of a faint idea of how much sand would be in a 50# bag. I would be very surprised if I removed more than about 70# of sand... and that is being VERY kind.
I have not experienced any sand in the pool in the few short years we have had it.
I did not see the guy fill up the filter. And from the care during the installation and operation of the pool for the first 2-3 years, I have no reason to doubt he did not fill it up correctly.
Can that much sand come out during backwashing?
Since I don't know exactly how much sand the owner's manual says to use.... how far below the center pipe should I fill the sand to?
Also, I'm using zeosand/zeolite.... forgot the name of it. I know it doesn't take as much as regular pool sand. But does that mean that volume wise it uses less but looks the same? Or do I fill it even less full compared to the center pipe?
Hope this questions make sense.