Sand, Cartridge & DE Filters
Sand is the oldest and most popular method of filtration.
Sand filters share two things in common:
- When in the filtration mode, water always flows from top to bottom
- 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 separate
particles, allowing filtration to take place. They operate on the basis of "depth"
filtration where dirt is driven through the sand bed and trapped in the spaces
between the sand particles. Initially, a clean sand bed removes larger particles,
and then, as the bed starts to load up with dirt, the filter removes finer particles.
The sand can be cleaned by backwashing which involves reversing water flow through
the filter to the "waste" line.
Internal view of a sand filter
Cartridge filtration has been available for a relatively
long time, but has only recently begun to enjoy rapid growth and acceptance.
When water passes through a cartridge filter, dirt is screened out at the surface
of the cartridge element. When clean, the element will trap larger particles,
with finer particles being filtered out as the pores of the element become clogged
by the larger debris. The cartridge element can be removed and cleaned by pressure
washing inside and out with a garden hose.
Internal view of a cartridge filter
Diatomaceous Earth Filter
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. 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 D.E. filters become dirty, they are 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.
For sparkling, clean pools; step up to Hayward D.E. filters.
Internal view of a vertical grid D.E. filter
Page Sand Filters
Pumps, Filters, etc
HOMEBUILT POOLS P.O.
Box 44455 Rio Rancho, NM 87174
(505) 898-7181 (603) 506-7677
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