I am living in my mom's house (she has Dementia), so I am unable to get too much information. It is 18 x 36. It was built around 1984 ish. It is a vinyl liner, in a small town, with most pool businesses that have gone out of business. I can't get the chlorine to register when I test it, but the water is crystal clear, and it looks great! I have been putting in about a gallon a day. I would guess about 30K gallons, but I don't know. It is inground and I am quite sure it is a sand filter system.
There is a hot tub business that will test water, and then recommend TONS of different things to buy. I would love advice from a swimming pool person. Maybe hot tub and pools are the same? I don't know. I have never cared for a pool. Thank you for any help!