By definition, a Micron is the space between 2 fibers. Generally speaking, the smaller the space the better the filtration. This is how filters are compared and sold. To put a Micron into something you can visualize, 1 grain of salt is about 100 microns. An average person can only see down to about 35 microns. My point has always been, does it matter if your filter can get down to 3 microns, you can’t see it any way, how will you know? Many are led to believe that the better the filtration the less chance of there being any disease causing bacteria in the water. The filter only filters out particles such as dirt, bacteria are killed with chlorine through sanitation not filtering.
SAND FILTERS have been in existence for a long time and generally do a good job starting off at 40 microns when clean and getting more efficient when dirt accumulates to around 20 microns. The problem with this reasoning–the dirtier the filter the better it works–is that as it gets dirty, it restricts the amount of water flowing through it. I would rather have a lot of water getting filtered good than a little water getting filtered better. A quick backwash and a sand filter will be operating back at around 40 microns. Backwash sand filters regularly, weekly is best, monthly at the least.
DE FILTERS or Diatomaceous Earth, filters down to 3 microns. The DE powder needs to be changed regularly and extreme caution should be taken when handling the powder as it can be harmful. Read the package and pay attention to the warnings–the powder is not good for you. Some areas now prohibit backwashed DE from being blown onto the lawn or down a sanitary drain. Drains can get plugged up from the DE, on the lawn the DE dries out and becomes a powder again–its not good for you.
In its wet form DE is an excellent filtering agent. In our pool service we change DE every 4 months. Always inspect the pool for any powder coming back into it, this could mean a tear in the media fabric or hole in other parts. DE should not be circulated back into the pool.
CARTRIDGE FILTERS strain at about 20 microns and as with sand filters, tend to get better when dirty, down to about 5 microns. But as with sand filters at what point does the dirt slow the circulation. We recommend keeping the cartridge clean and at DAD’s Pool we wash them weekly and multi-cartridge units monthly. We have a saying that a clean filter means a clean pool. Cartridges should last at least 2 years if cleaned regularly.
In our opinion, there are Good, Better and Best cartridges. Pleatco standard filter is a Good all-around filter. They can tear easily and may need to be changed more often. Unicel makes a Better and is the easiest to clean. Their media is folded like a “w” rather than than a “m”, meaning that folds don’t touch and allowing a stream of water to get deep into the folds for a good cleaning. And a Best is Pleatco with Microban, a sturdier media that holds up longer. There are other cartridges available and some are paper thin. Although they look the same, they are not.
To sum up, Sand Filters work well but only filter down to where a cartridge filter starts. DE filters the best, however, disposal and recharging of the DE is hazardous. Cartridge filters work well, are easy to clean and dispose of. We service all three but in my pool I use a cartridge. That’s my opinion.