Swimming pool filters
|In ground pool filters||Above ground pool filters|
| Cartridge - Cartridge
Diatomaceous Earth - Grid replacement
Many pool professionals consider D.E. filtration to be the finest, because it is capable of removing smaller particles than either sand or cartridge.
Diatomaceous earth is a porous powder with microscopic openings, that, when magnified, look like tiny sponges. Clear water can pass through these openings, but particles, as small as one to three microns, are trapped during the first pass through the media.
All D.E. filters have internal elements that become coated with D.E. It is this 'filter cake' that strains dirt, dust, algae and some forms of bacteria from the water.
Similar to sand filters, when a D.E. filter becomes dirty, it is cleaned either by backwashing, or regenerating and draining, the clogged D.E. to the 'waste' line. To restore filtration, a fresh 'charge' of D.E. is added to the filter.
The oldest and most popular method of filtration is sand. Sand filters share two things in common: 1) When in the filtration mode, water always flows from top to bottom; 2) They all have some sort of lateral or under drain with slots to hold back sand while allowing clean, filtered water to pass through.
High-rate sand filters use a special filter sand, normally .45 to .55 mm (also known as pool grade #20 silica sand), because it has sharp edges that serve to separate particles, allowing filtration to take place. They operate on the basis of "depth" filtration; dirt is driven through the sand bed and trapped in the minute spaces between the particles of sand. Initially, a clean sand bed will remove larger particles, and then, as the bed starts to load up with dirt, it will remove finer particles.
Cleaning of the media, or sand, is accomplished through reversing the flow through the filter, to the "waste" line. This is known as backwashing.
|Summaries courtesy Hayward Pool Products|