dfullwood

I bought a house with a pool that has a Heldor Pureflo Hi Rate Sand filter. I can find no references to this company or filter online. I believe the company may have gone out of business. I suspect the filter is about 15years old. Can anyone tell me how much sand or Zeobest I would need to replace the sand currently in it? The Filter is fiberglass and measures 26 inches from the ground (sitting on a base ring) to the top, with a 67 inch circumference in middle. Any insight would be appreciated. dfullwood1@charter.net