[alisasny]

How often should sand be changed. I have heard that if filter is working properly it should be every 5 years as it works more efficient when it has dirt in it.

I have another friend who changes it yearly.

[azhenfud]

"How often should sand be changed."

SOME "experts" claim every other year - some every five years. Since my dad has been in the business for four decades, I've never heard him advise anyone to "change" the filter medium in a sand filter. However, when a system is backwashed and when winterized, it's normal to lose some sand, which - over time - could equal a significant amount that must be replaced at some point.

I've owned a pool for thirty years and I never have "changed" the sand. The sand in a filter isn't like the sand used to sandblast in that the sharpness isn't worn off by use as rapidly. So the idea that the sand is "worn out" is a myth and since most filters are hard piped into the system, it requires a "hugh" service call ($100-200) to "change" the sand ($1.75).

[Squeako]

Unless you have a large sand filter typically used on large commercial pools (with actual sand), you probably mean the filter medium which is most often Diatomacious Earth or "DE". When I was cleaning pools for a living, I had them regularly scheduled about every six months or when the pressure hit 35PSI, but that's in California where the filters are running year-round. It involves taking the lid off the filter tank, removing the ribs, hosing them off and replacing any broken/torn pieces. If you don't let the pressure get too high (over 30PSI), you most likely won't have anything broken. If your pressure isn't too high and you have a good flow rate (can't remember the recommended safe minimum) there doesn't seem to be any reason to change it since it's doing what it's supposed to.

The dirtier the pool, the more crap that gets trapped and the pressure goes up/flow goes down. You'll notice that when you're trying to vacuum it becomes difficult to pick anything up. Backwashing the filter helps temporarily, but if it's really dirty the only thing to do is clean it. Personally, I never used DE in any pool I serviced because it is nasty and leaves white powder on everything. Try CF-138 (trying to recall the exact name) which is a cellulose fiber and is a heck of a lot less messy since it degrades like biomass (which will include all those skin cells from the pool).