The reason our swimming pools stay crystal clear is due to a number of things.  First of all, correct water chemistry will ensure our water stays clear and algae free.  But another important factor in keeping our equipment running at it's highest efficiency is making sure to periodically clean the filter cartridges.  You see, every little particle of dirt, debris and even our skin particles that flake off while we swim are all captured by the pool filter.  It does an amazing job at catching particles so small, they're barely visible to the human eyes.  Often the out of sight, out of mind concept happens with our filters.  We don't see them because they're sealed in this big tank and we have no idea how dirty they really are.  The only accurate means of keeping track of how dirty they are is to start a log.  When we clean the filters, we need to record in a journal the exact water pressure in the tank.  And as the filter does it's job and catches all of the gunk in our pool, the tank pressure slowly climbs.  If you read manufacturer's suggested time to clean filters they usually will say to do it when tank pressure is 10 lbs above start-up pressure.  But with most pools, the filters will go way too long and be functioning at a much less than efficient capacity if we wait that long.  With the newer filters, we can typically clean filters twice a year; Once in the spring to get the pool ready for summer and once in the winter.  The filter capacity is measured by square feet.  Most newer filters are around 400 sq ft.  They contain 4 very large cartridges that need to be removed and sprayed off with a garden hose.  Don't use a pressure washer, as it can damage the cartridges.  It requires a little patience because it takes some time to get deep into the filter pleats with the water and remove the debris.  Some of the older filters are much smaller than the new ones and will require cleaning on a more regular basis.  A lot of the smaller ones only have one filter cartridge or 4 small ones.  Some of the older ones have 2 cartridges, one on top of the other.  Either way, they will have to be cleaned out more frequently.  Once a quarter is good for most, but the really small ones will have to be sprayed out once a month.  The other thing to remember when cleaning your pool filters is once the cartridges are removed from the tank, the tank will also have to be cleaned out.  It will have a drain plug on the bottom and it will need to be removed and the tank sprayed out.  Also, around the center of the filter tank you will find a large, black o-ring that will have to be cleaned and relubricated with the proper silicone lube.  The cleaning of filter cartridges can be a bit tedious, but will ensure that the pool stays clean and that the chance of algae rearing it's ugly head is minimized.  If you get stuck or simply don't want to deal with it, give us a call and we'd be happy to help out.