Hi. I’m from Argentina. I have a Hayward S200 filter from over 30 years back and decided to change the sand. I disassembled the whole top access cover, unbolting everything since the top diffuser was stuck and I didn’t want to force it. I’ve owned the house 34 years with extremely hard well water and never changed the sand. Everything was rock solid with scale, but I put in 7 quarts of white vinegar and let it sit overnight and slowly chipped at the “sand” loosened it and scooped it out.
I discovered that underneath the sand there were pebbles about 1/2 to 3/4 inch covering the laterals up to the bottom Internal Elbow Pipe and from there the sand. Is that an OK arrangement and can I replicate this on my sand change?
Yes, using pea stone in the filter is a common base layer. Though it’s not completely necessary and the filter could be filled exclusively with sand. So that is up to you!