I spent Sunday changing out 300 pounds of sand in my filter and thought I would pass on some tips I learned along the way. I completely forgot to take pictures, but really there wasn't much to see.
This is my filter:
The filter has a date stamp of 1995 on it, and we bought the house three years ago. I wouldn't doubt if the sand was original. The filter worked OK, but the unknown quality of the sand always bugged me.
I didn't even shut down my pump...I just placed it on Recirculate. After opening the drain plug and popping the top, I realized that digging the sand out by hand was an exercise in insanity. So I got my shop-vac out and used those long rigid extension tubes to suck out the sand. It was slow going vacuuming up wet, nasty sand, but it was MUCH faster than digging it all out by hand. You just have to pause often to empty the vac. After a couple hours I made it down to the laterals, all of which were in good shape (Whew!). I would periodically take a garden hose and wash down the inside of the filter to get as much sand as I could out. I couldn't get it all, so there was probably 1/2" or so of old sand in the bottom, under the laterals. The shop vac actually worked better if there was some water in the tank. It had better "suckage" on slurry then moist sand. I was stunned at the nastiness of the sand. There was SO much junk and clumps that weren't getting backwashed out.
To re-fill, I just took a plastic cup and placed it upside down over the inlet pipe so sand wouldn't get into it. I then filled up the filter with water about halfway to help cushion the laterals from the incoming sand. The first two 50# bags I poured very slowly, reaching in and leveling it out with my hand. After the laterals were covered I poured the next four bags much faster, still leveling after each bag.
After buttoning it all up, I backwashed the new sand for a good five minutes. I thought I would have to go much longer, but the water ran clear quickly. Then a few minutes on "rinse" to settle everything out and back to filter.
The first thing I noticed was the pressure drop with the new sand. My starting pressure was 16 with the old sand and I would backwash at 21. The new sand pressure was 12.5. I considered going with Zeolite, but have always been perfectly happy with good old sand and just couldn't see paying the extra $$$.
I thought this was really going to be a big chore, but it was actually VERY easy. If this is on your "Pool To-Do" list and you have a shop-vac, it's a 3 out of 10 on the difficulty scale. Just be prepared to spend all afternoon doing it.