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Filters: Types and Capabilities
Some of the most commonly asked questions regarding pool
filters are:
- What kinds are there?
- What are the differences?
- Is one more efficient than another?
- When installing a new filter or replacing an old one, which filter do you
recommend that I use?
We offer the following information to answer
these questions and hope that it may be helpful to you in understanding the
issues and our recommendation.
Sand Filters:
The outside of this type of filter is usually made out of fiberglass or
stainless steel, and it is partially filled with silica sand. As water
circulates from the pool through the filter, water enters at the top and
percolates downward, leaving most of the oils, debris, and other impurities
trapped in the sand, thus allowing clean water to return to the pool.
The filter is usually backwashed once per week, a process which
reverses the flow of water through the filter. This lifts most of the
contaminants from the sand and washes them out the backwash line, along with a
volume of water. Eventually the filter becomes overburdened from minerals in the
water and from the volume of debris (dirt, dead algae and bacteria, etc.)
remaining in the sand, causing the sand to be hard and compacted. This reduces
water flow throughout the system, and can cause cloudy water, poor heater
operation, and increased wear and tear on the pump. Approximately every 3 to 5
years the old sand will need to be removed, and new sand added. If the pool is
painted, the sand may need to be changed annually.
The efficiency of the sand filter, as measured by the largest-sized
particle that can pass through it without being caught, is 40-50 microns. (A
micron is a millionth of a meter.) In the past, more sand filters have been
installed in some areas because of the supposed "ease of use" for the
pool owner, but drawbacks of the sand filter include:
- Longer hours of operation are required to properly filter the pool water
- Filtration efficiency (compared to other types of filters) is inferior,
especially in hot climates
- Higher chlorine levels are usually required on pools with sand filters to
help reduce the risk of the pool water turning green
- Because of frequent high-flow backwashing, this type of filter wastes more
water
- Since homeowners rarely see the inside of the filter, and since the sand
usually lasts for years, maintenance on sand filters is frequently neglected
A new sand replacement product called FiltraMax eliminates most of the
disadvantages of a sand filter. FiltraMax will filter particles as small as 1
to 5 microns, ten times more efficiently than regular sand. It also eliminates
ammonia to prevent the formation of chloramines which causes burning eyes,
stinky chlorine smell and robs your chlorine of its effectiveness. Please call
us with questions or visit FitraMax's web site
here.
Cartridge
Filters:
Cartridge filters come in various sizes and shapes. Most
of the filter canisters (or tanks) are stainless steel, but some are made of a
hard plastic or fiberglass. There may be as few as one or as many as fifteen or
more cartridge elements inside a cartridge filter. The cartridge elements are
cylindrical, and made of a paper-like fiber. As the water passes through the
elements, impurities are collected on the element material. Cartridges remove
smaller debris from the water than sand; its micron rating is about 20 microns.
This filter is cleaned about once a week by removing the elements from the
canister and hosing it off using a high pressure nozzle.
Drawbacks for the cartridge filter include:
- Most cartridge filters are for smaller pools and spas containing
approximately 12,000 gallons of water or less
- There is no mechanical method for backwashing these filters - it must be
done by manually disassembling the filter and hosing it off weekly
- The cartridge elements need to be replaced as they become old and worn:
about every 2 years, which can be expensive, depending on the size, style and
brand of cartridge
- Pools with cartridge filters tend to develop high dissolved solids levels
(TDS) faster than sand or D.E. filters, because there is no water removal via
backwashing.
D.E. (Diatomaceons Earth) Filters:
The
majority of D.E. tilters are made of stainless steel, with a few being made of
fiberglass. The elements inside consist of a series of plastic grids covered
with a cheesecloth-like fabric. A white powder, known as D.E., is added through
the skimmer and mixes with the water as it heads toward the filter. As the water
passes through the filter, the D.E. powder coats the outside of the elements.
This coating traps microscopic impurities which cannot be trapped by sand or
cartridge filters, and therefore provides better water clarity in the pool. The
efficiency rating of a D.E. filter is about 3 microns. This means you can filter
anywhere from 15% to 50% less per day, which results in reduced electric bills,
and extended motor life.
Especially in drought areas, D.E. filters are most commonly
recommended and installed because of the lower water requirements for cleaning
(compared to the sand filter).
Drawbacks for the D.E. Filter:
- To clean this type offilter, the filter must be taken apart in order to
hose the elements off with water. Each time you backwash, or clean the grids,
you need to re-charge the filter by adding two to four pounds ofthe D.E. powder
(which is very inexpensive) through the skimmer. However, since modern D.E.
filters can go as long as 6 months to a year between cleanings, this is not much
of a drawback! Older D.E. filters usually are cleaned quarterly
Summary and Recommendation:
If you pose the
questions at the start of this bulletin to someone who doesn't regularly
maintain swimming pools, you might receive a wide range and variety of answers.
But if you ask a trained service technician who services pools daily, and who is
responsible for the cleanliness of your pool and the clarity of the water, you
will consistently hear the same answer: D.E. filters (Diatomaceous Earth) are
the best! If your filter is working fine, there is obviously no need to replace
it, but if you are faced with the need to install a new filter or replace an old
one, please consider the following points:
- All three types of filters are used within the pool industry. The warmer
the pool water becomes, the more efficient the filter needs to be. Sand and
cartridge filters work best in cooler climates, but in the western states, where
pool water temperatures often reach the 90's, they aren't nearly as effective as
D.E. filters.
- The cost differences between the sand and D.E. filters are minimal, with
cartridge filters being the least expensive. If you are looking for dollar value
without headaches, the D.E. filter will give you that and more!
- A D.E. filter requires less time and effort to maintain in optimum working
condition. Although most problems experienced by sand and cartridge filter
owners are caused by improper maintenance, even a perfectly maintained cartridge
or sand filter cannot match the efficiency ofa D.E. filter.
- As measured by the size of particle it can remove, a D.E. filter is 7 times
more efficient than a cartridge filter, and 15 times more efficient than a sand
filter.
- A D.E. filter is the best choice for those who must keep the pool clean and
clear, for those who swim in the water, and for those who enjoy the look of
sparkling, crystal clear water in their backyard pool.
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