Tech Notes: Sand Filters

I write this blog with icicles hanging from my nose, but I know in the near future (at least I’m crossing my fingers), pollen will be in the air.  I can’t believe that I would ever be hoping for pollen, but that means warmer temperatures, right?  All filters get pretty clogged up with pollen during the spring season, but I will address sand filters more here.

Sand filters are more than just normal sand.  In fact, a couple years ago, we had a customer who added play sand into their filter doing their own sand change and discovered the difference.  Filter sand is a very jagged sand whereas play sand is rounded.  Now if you don’t like your kids much, you can put filter sand in their sand box and have them come in the house crying that they have sand splinters stuck in their skin, but this is not recommended by either us or the division of family services.  The reason for the course sand in filters is just as you would expect, course sand catches debris, whereas rounded sand allows dirt to roll right off of it.  Of course cleaning course / jagged sand takes more than just a rinse to get the dirt off of it, water in the filter reverses and puffs up this sanded, agitating it and allowing these dirt particles to come off.  Among these dirt particles is the pollen, which is a major source of filter loading during the spring months.

There are times when your filter needs to be backwashed more often.  Right when the pool is started up, you have much debris that has settled into your pool.  All of this debris does not go directly to your filter, but is slowly loaded as the pump system continues to blow water over the pool surface.  When bathers get into the pool and jump up and down in the pool, this agitates the material on the bottom of the pool and sends it towards the filter through the suction fittings.  During these times, your filter may have to be backwashed more often.  As a rule of thumb, after a pool is backwashed, the filter is considered “clean”.  When the PSI gauge (yes, we know that these break often… remember, we don’t make them, just install them) goes up by about 8 – 10 PSI, it is time to backwash your filter again.  How long does this take for that to happen?  Well, I wish there was a perfect answer for this.  If you have a smaller filter, it will load faster.  It there is a lot of dirt, it will load faster.  If there is a lot of pollen in the air, it will load faster.  If you had your kids baseball team come over to shower after their tournament, it will load faster.

Maintaining all of your equipment and your water chemistry will not only keep your filter running more efficiently, but your entire equipment system and pool structure.  Over time, those jagged pieces of sand start to loose their “rough around the edges” look… and let’s face it, who wants wimpy sand?  So sand, while a long lasting media, is a media that eventually needs to be replaced.  How often you ask, well again, this depends on how small the filter is, type of sand (there is river sand, silica sand, zeo-type sands, glass media, etc).  The most popular one is probably the silica sand and it is fairly inexpensive (more than river sand however).  It does a great job, especially on pools that have enhanced filtration (such as ClearPro technology).  We could go on forever talking about different parts of sand filters, but then you wouldn’t call us… you would just read our stupid blogs… and we love to hear from our customers…

So if you have further questions about your sand filter, or are simply board out of your gourd, give us a call and we will totally geek you out telling you about all that we know about sand filters, micron removal, multipart valves, channeling, mud tests, etc, etc, etc.  If it has been over 5 years since your last sand change however, the National Swimming Pool Foundation ( does recommend changing your media about every 5 years.  You can probably go longer than that, but if it has been 10 years, I’d say that you are pushing the limits… go ahead and give us a shout… or if doing it yourself, don’t use play sand!

Happy Swimming!
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