What's the Best Type of Filter for Your Pool?

There are two major types of filters for home pool use: sand filters, and diatomaceous earth filters.

First of all, what are they?

Sand filters use sand that has been graded to a range of 45 to 55 millimeters. This specially graded sand traps water impurities as small as 20 microns.

Whereas DE filters use "diatomaceous earth," which gets its name from diatoms, tiny sea creatures that fall to the bottom of the ocean when they die. Eons later, when the land lifts out of the sea, we can often see chalky cliffs made almost entirely of this diatomaceous earth--like the Cliffs of Dover in England.

DE is much finer than sand, capturing debris down to around 5 microns--which is incredibly tiny!

So you'd think, why not get a DE filter to filter out the most impurities?

Well, one downside of the DE filters is that they're more expensive; plus because they are made with such fine material, they tend to get clogged more easily, so they're a bit more temperamental and take more attention and maintenance than sand.

Whereas, one of the plus sides of a sand filter is that its efficiency actually increases over time. You might assume that your filter would stop working as well as it captures more debris. But as it collects more material from a number of cycles, your filter will capture even more bacteria and other impurities.

Sand filters may remove more and more debris for a while, but eventually they get too full, and the pressure begins to rise. The filter has a pressure gauge, so you can tell when it's time to backwash and get rid of the accumulated debris. You should always backwash once the gauge gets to around 8 to 10. Backwashing provides your filter a fresh start, and can be repeated regularly for several years.

Of course, eventually it will get too full, despite all the backwashing you've done, and you'll have to backwash more often. Keep track of your pressure gauge and how frequently you backwash. When it gets to the point where you have to backwash every week or two, you may need to replace the sand.

Sand-based filters are simple and easy to maintain. However, one of the downsides is that it may take longer to clear up a cloudy swimming pool, or one that's been attacked by an algae bloom--whereas a DE filter can attack these problems more quickly. So the secret is to keep on top of these issues in the first place! Which an above-ground sand filter makes it easy and convenient to do.

Bottom line: sand-based filters are fairly low-maintenance compared with DE filters. Public pools often use them, and water treatment plants use really huge sand filters to treat a whole city's water. Your own tap water is likely purified this way. Add up the pros and cons and see which is the better option for you!