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Sand filters remove the largest
particles, Cartridge filters remove smaller particles & DE filters remove the
smallest.
Let's look at the 3 types of filters & how they work.
Sand
filters. All sand filters have 3 things in common as to their performance:
1. they all use sand (some older filters may use a combination of sand &
gravel). 2. Dirty water enters in the top of the filter tank & flows down
through the sand which filters out the dirt & debris (down to a size of about 25
- 40 microns - visible dirt & debris). 3. Cleaner, filtered water is
collected at the bottom of the filter tank & pushed out of the filter & returned
to the pool.
Sand filters are the oldest form of pool filtration or water
filtration for that matter. Even ancient civilizations used sand as a
filter to cleanse water & help make it more potable (drinkable).
Sand filters have been the most common filters used in the
swimming pool industry until recently. These filters are great when using
non-chlorine sanitizing products such as biguanides (i.e. BioGuard Soft Swim or
Arch Chemicals Baquacil). For most people, sand filters will perform a
very adequate job.
Drawbacks: more time needed to filter out fine particles;
lots of water (sometimes hundreds of gallons) is "wasted" when backwashing or
cleaning the filter by reversing the flow of water inside the tank; sand is
heavy.
Care of Sand filters: Backwash only when needed - a dirty
sand filter pulls out a finer particle - usually no more than once a week.
Chemically clean the filter about 2 times per season (after initial cleaning &
at mid season) to break up & remove accumulated greases, oils & dirt that has
become embedded in the sand. Change the sand about every 3 - 5 swimming seasons
(one season equals about 4 - 6 months) - sand crystals lose their "sharpness" &
are not as well able to trap dirt & debris.
Please review the
note on Chemical Cleaning below.

Cartridge Filters. Like sand filters, all cartridge
filters have 3 things in common: 1. They all use some type of pleated fiber
cartridge. 2. Dirty water enters in to the filter tank & flows through the
cartridge which filters out the dirt & debris (down to a size of about 10 - 20
microns - much smaller, but still visible dirt & debris & some algae). 3.
Cleaner, filtered water is collected on the other side of the cartridge & pushed
out of the filter & returned to the pool. Some folks notice a cleaner
difference compared to sand filters.
At one time, cartridge filters were only popular in the sunbelt
areas. Today, they are used in all parts of the country on all kinds &
styles of pools. Cartridge filters can be used with any pool sanitizing system.
Because of their relatively large filter surface area (the pleated fiber
material can be as large as several hundred square feet as compared to under 4
square feet in the largest residential sand filter), cartridge filters generally
take a long time to get dirty between cleanings. A properly sized filter may
only need to be cleaned 2 or 3 times per season. When sized right, less
vacuuming may be needed due to the finer filtration.
As with all filters, sizing it properly is critical. Never
undersize. Never. This is a true case for the axiom, "you get what
you pay for." An undersized cartridge filter MAY initially do the job,
according to the sizing charts, but in short time you will be disappointed in
the performance of the filter and in the amount of work you now need to do.
Drawbacks: Proper sizing of the filter to do the proper
job. Trying to use an aboveground filter on an inground pool. Filter must
be disassembled & cleaned about once each month.
Care of Cartridge Filters: Clean only when needed.
Usually about once each month. Cleaning is accomplished by taking the filter
apart & hosing off the accumulated dirt & debris from the cartridge. Chemically
clean 2 times per season to (after initial cleaning & at mid season) to break up
& remove accumulated greases, oils & dirt that has become embedded in the
cartridge material. Replace the cartridge about every 3 - 5 swimming seasons
(one season equals about 4 - 6 months).
Please review the
note on Chemical Cleaning below.
DE
Filters. DE or Diatomaceous Earth filters offer the finest filtration
available. DE filters use grids or "fingers" called septums that hold DE
(fossilized microorganisms) that has the properties of a fine but gritty powder.
DE filters have the ability to filter particles as small as 2 - 5 microns in
size (the size of algae & even some large bacteria).
Water goes into the filter & passes through the DE coated septum.
Under a microscope, DE looks like little sponges with tiny holes & nooks &
crannies that trap all kinds of stuff. The clean water is then collected &
returned back to your pool.
In many places you can or are urged to use DE replacements, such
as Aqua Pearl, which are lighter in weight & more biodegradable than DE.
Especially compared to sand filters, you don't get just filtered water, you get
polished water.
DE filters eliminate many pool care problems because of the
superior filtration. A DE filter has the capability to take a dark green,
algae encrusted pool & turn it into a crystal clear paradise in a matter of a
few days. Many pool owners notice how less often they "need" to vacuum the pool.
However, there is more care needed in maintaining a DE filter.
Drawbacks: DE filters tend to clog up easier - partially a
function of the fine filtration ability. If you have a really dirty pool,
the filter may clog up every couple of hours & you may have to change the DE.
That's normal. However, you will reap the clarity results in much less time.
The other drawback is the waste or used DE. In many municipalities it is
considered a hazard waste material & therefore needs to be treated as such.
Check your local authorities for details.
Care of DE Filters: Clean only when needed. Some DE
filters come with backwash valves while others need to be "bumped". Physically
clean (2 times per season) the filter by taking the filter apart & hosing off
the accumulated dirt & debris from the grids or fingers - backwashing or bumping
may not fully remove the used DE. Chemically clean the filter 2 times per season
(after initial cleaning & at mid season) to break up & remove accumulated
greases, oils & dirt that has become embedded in the septum material. If
regularly chemically cleaned, the grids should provide a life of, 7 years or
more. Please review the note on Chemical Cleaning below.
Filter your water for 8 to 12 hours every day from opening to
closing. Use a timer so that you don't forget and save money. By the way, for
the best filtration, be sure to chemically clean your filter about twice each
season to remove accumulations of greases, oils & other swimmer and
environmental waste that clog your pool filter & that routine backwashing &
rinsing will NOT remove.
Why you need to Chemically Clean your
filter: As noted just above, chemical cleaning of your filter aids
removing greases, oils & other swimmer and environmental waste that will soil
your filter and shorten its life. Normal, regular backwashing & rinsing
will not remove these wastes. Here's a couple of analogies that will help
you understand the significance of chemical cleaning: do you use shampoo on when
you wash your hair or do you just rinse it? Without shampoo, your hair
would be pretty matted & dirty after a couple of weeks. How about dirty
clothes? Do you only rinse them out in the washing machine or do you add
detergent to release & help remove the dirt & greasy stains? The same
thing goes with your pool filter.
How do you chemically clean a filter?
That's easy. Use
filter
cleaning products such as
BioGuard®
Strip Kwik® that is
used when you can soak your filter (soak the elements or it can be backwashed
into a sand filter) for a several hours. Spray on products such as
BioGuard®
Kleen It® work
quickly to remove ground in dirt & oils.
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