Some pool owners leave the sand in their filter indefinitely and rely on backwashing to keep it clean, but they are the exception. Filter manufacturers and pool maintenance pros recommend changing it every five years to ensure you get the maximum performance from the filter. Some filters hold 300 or more pounds of sand, which is a lot to cart to some off-site disposal area. Because the filter has to be changed so infrequently, it's fairly easy to find ways to use the old sand around the house and save yourself this trouble. Just don't use it in sandboxes or other areas in which children or pets might play.
Pool Sand Is Not Play Sand
One problem with using pool sand in play areas is the danger from contaminants the sand has collected from the pool water. They are the same contaminants you come in contact with whenever you get in the pool, but pool sand contains a much larger concentration of them. They could pose a health risk.
Another problem is the composition of the sand itself. Rather than containing a whole host of minerals, as beach and play sands do, pool sand primarily consists of crushed silica quartz. The dust from this type of sand is a Class 1A carcinogen that can cause a fatal lung condition called silicosis. This is obviously not something in which you want your children to play. It's isn't safe for pets either and is not the best choice of fillers for cat litter boxes.
It Isn't Concrete Sand, Either: It isn't a good idea to incorporate used pool filter sand into a concrete or mortar mix because the material from which it's made weakens the concrete mix. Concrete sand is composed mostly from crushed limestone and granite, which are harder materials than silica quartz.
Use Pool Sand for Landscaping
The granules in pool sand are less than a millimeter in diameter, and may be much smaller. This fine mixture is great as an underlayment for paving stones as well as filler between the stones. You can also use it to fill holes in the lawn or garden or to spread on the surface of existing dirt pathways. None of these applications expose you to the possibility of inhaling silica dust or pool contaminants.
Save Pool Sand for the Winter
The average pool filter contains the equivalent of about seven bags of sand, which is more than enough to keep your walkways and steps slip-resistant for one or two winters. Store the sand in covered 5-gallon buckets. Each bucket holds about as much as one bag.
Because of the contaminants it contains, pool sand should never be left in a pile in the yard. If you can't find a use for it around the house and you don't want to truck it to a disposal site, the best way to deal with it is to dig a hole in the yard or garden and bury it. If you choose this option, be sure you locate it far from drainage areas, because flowing water will wash it into the ground, and the soil covering the hole will collapse, leaving a depression that you'll have to cover with more topsoil.