DD & SIL purchased a 20 year old home with a pool and spa that I am guessing is about the same age as the home.
Pool has a Triton sand filter. SIL decided he wanted to change the sand in it. He called the business that serviced the pool equipment for the former owner to find out information about it. They told him, you don't change the sand in that filter. It is a disposable sand filter. You just replace the entire filter every 8 to 10 years. They pulled up the records and told him the filter was installed about 7 years ago.
Does that sound right? I didn't know there was such a sand filter that you couldn't change the sand. I googled a bit and couldn't find anything regarding a disposable sand filter. To me, on the outside, it looks identical to every picture I've found of even the newest Triton II filters.