Sand filters capture particles down to 20-40 microns.
A slightly dirty sand filter works better at capturing and filtering stuff. Only backwash when your filter pressure raises 25% over your baseline clean pressure.
Adding a small amount of DE (diatomaceous Earth) can improve the filtering capability of a sand filter. Pool grade DE should be used, food, pet or garden grade will not work.
Sand and Alterative Media
The sand in a pool sand filter is #20 silica sand; 45 - 55 mm. A discussion about different qualities of pool sand can be found in My findings on how not all sand is created equal. Pool sand that is too fine with small particles will be blown out from the laterals.
Pentair uses US Silica Mystic White II sand for all of their testing. It may not be readily available at Ace/Home Depot though. In general, we recommend getting your pool sand from a pool supply store and not a hardware store as they are far more likely to stand behind what they sell than a big box store.
Be aware that members have had issues with Quiikrete pool sand. A search in the Forum can provide more information about the issues.
TFP recommends using pool sand. There is no need for an alternative media like glass.
How to Deep Clean a Sand Filter?
Deep Cleaning a Sand Filter has instructions with pics of the deep cleaning process.
My sand is "channeled" how to fix it?
- Open up the filter so the sand bed is exposed.
- Stick a garden hose into the sand and turn on the water. The sand should loosen up and all the dirt and gunk should float and overflow out of the filter.
- You might need to stir up the sand a bit. Keep this up until the water overflowing out of the filter is clean.
- If any sand is clumped together CAREFULLY break it up with something like a broom handle but BE VERY CAREFUL NOT TO DAMAGE THE LATERALS. You will be surprised at how much stuff this gets out of your filter that backwashing doesn't and I feel this 'deep cleaning' should be done yearly.
- This should take care of the channeling but if the sand has a lot of calcium deposits you might want to follow this up with an acidic sand filter cleaner from the pool store.
- GENTLY tap on the sand tank with a rubber mallot and watch the pressure gauge climb about 2 psi.