As a part of my pool opening this year (5 year old pool, 2nd season owning it) I decided to pop the top of my sand filter and see how things looked. I've read that you should consider changing the sand after 5 years and I wanted to see the general condition of the filters internals.
The multi valve came off easily enough and the first thing I noticed was the fliter housing was about 1/2 full of sand and there were THOUSANDS of ants that had decided the sand filter was a great place to build their nest this year. I knew the ants would get washed out on backwash, but I had no idea if the sand was at the correct level. Other than that everything appeared normal.
I decided to vacuum out the ants then top it up with new sand. At that point I realized i had no way to measure the amount of sand I was removing so the decision was made to replace all of it. That turned out to be a decent decision; as I continued to vacuum the sand started to smell pretty awful. Then it got very awful towards the bottom of the filter - it smelled like cat poop, if that cat was on a strict blue cheese diet
I rinsed the entire filter housing and washed out the laterals then off to the pool store for 300lbs and ($57) worth of fresh filter sand.
I filled the filter about 1/2 way with water then replaced the laterals. I didn't have a cover for the tube that leads down to the laterals so I covered the hole with one hand and covered the tube with the other. I did about 2 of the 50lbs bags that way, then figured out I could rest the upopened bag on top of the filter then make a small slit in the bag, away from the tube. That process worked well, and I had more control over the distribution of the sand.
Once I had loaded all 300lbs I realized that filter was just over 3/4 of the way full w/ sand. The filter was approximatly missing approx 75 to 100lbs of sand before I stared. Everything went back together without issue. I set the valve to backwash and I fired up the pump. Backwashed for 3 min, rinsed for 1 min then backwashed for another 3min.
Before I started the pump on with the "Fliter" setting I noticed my pressure gauge was sitting @ 5psi. Time for a new pressure gauge
Everything fired right up, but I have no accurate way to judge if the nominal pool pressure is up or down. On average it operates around 22psi - I'm curious how the extra sand will effect the nominal pressure.
All around it was an easy process. I'm glad I got the ants and the funky smelling sand out of there. I think it was well worth the 2 hours of effort and $57 worth of sand.