by Mark Garcia March 09, 2016
In-Ground Pools can use sand or cartridge filters, but if you want the best filtration possible, a D.E. filter is the way to go.
Diatomaceous Earth pool filters remove particles under 3 microns, which far exceeds the capability of sand (20-40 microns) or cartridge (10-20 microns) filters. This can allow you to run the pump less, or use fewer chemicals, clean up adverse water conditions fast - or avoid them altogether.
If you are in the market for a new pool filter, today's blog post is a comparison of DE pool filters for inground pools of 20-50,000 gallons.
DE pool filters are available in 4 grid styles. DE grids are the elements inside the tank which are coated with DE powder. Grids are not the filter, but serve as the 'holder' for the DE powder, which does the filtering of the water. These Grid Styles are 'Finger', 'Curved', 'Straight' and 'Cartridge'.
This style of DE filter grid is patented by Hayward, and used on the Perflex line of DE filters. Called Flex-Tubes by Hayward, and called 'fingers' by most everyone I know, these 16in long tubes are about 1/2in wide and arranged in a concentric circle pattern. Having over 100 tubes creates a large amount of surface area (40 sq ft) in a small package, called the Flex-Tube Nest, shown here. Another unique feature of the Perflex line of filters are their unique 'Bump Handle', which is used to bump the Flex-Tube Nest assembly, sloughing off and mixing the DE powder and dirt, to reduce filter pressure. This can result in longer filter cycles, or times between changing the DE powder. The Perflex filter is not backwashed, but is flushed and drained periodically.
Considered the standard grid design, the curved grid assembly may also be the most popular, or certainly the most used grid type. Slightly curved grids are arranged in a concentric circle pattern, held in place by long thru-bolts that pull the bottom plate and the top manifold tightly together. The curved design conserves space within the tank, and uses only two sizes of grids, 7 full grids, and one partial grid which is half as wide, to fit behind the standpipe. These filters are used with a backwash valve, either a side mount multiport valve or push-pull valve, for high pressure removal of dirt and de powder, before re-charging the filter with fresh DE powder. They can also be 'bumped', or backwashed for 10 seconds, to conserve water by lengthening the time between backwashes.
Straight DE grids are not curved, but are flat rectanglular panels, covered with the same polypropylene mesh material. Proponents of straight grid DE filters point to less bridging of DE powder between neighboring grids and more balanced flow inside the tank, resulting in lower filter pressure and higher flow rates during filter and backwash cycles. They are also easier to clean with a garden hose (required once or twice per year for all DE filter), than other DE grid types. The Sta-Rite SD filter is the only remaining company to still produce a flat grid DE pool filter, and I sometimes wonder why!
When DE pool filter manufacturers noticed cartridge pool filter owners using DE powder as a way to improve filter performance, they struck upon an idea and created cylindrical DE grids that looked like a filter cartridge, but with made with different materials that allow greater flow rates and longer filter cycles. The Cartridge DE grid material is made from woven polyester in a thicker weave. Cartridge DE filters are backwashed easily and completely, or rinsed off with a hose if you want to save water. The slick surface and wider pleats are easy to clean, and don't even have to be removed from the tank.
So there you have it - 4 ways to filter your pool using DE powder. If you want to know my favorite, I would have to say that they are all terrific, but if given a choice, I'd go with the Hayward or Pentair curved grid design. It's a simple design, with cheap and easily available parts. But all of these DE filters have some advantages, so whichever grid type, brand or color you choose - it's sure to improve your water quality!
Thanks for Reading!