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 some of the variables to consider in choosing a swimming pool filter.
SAND FILTERS :
The outside of this type of filter is usually made out of fiberglass or plastic composite, and it is partially filled with silica sand. As water circulates for 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 one or two times per month, a process that reverses the flow of water through the filter. This lifts most of the contaminates from the sand and flushes them out the backwash line, along with significant amount of water. The efficiency of any filter is measured by micron size (one millionth of a meter) by the larges micron that can pass through the filter with out being caught. Sand filter efficiency is 40-50 microns. Eventually the filter can become overburdened from the minerals in the water and from the volume of debris (dirt, dead algae and bacteria, etc.) remaining in the sand, causing the sand to become hard and compacted. This reduces water flow throughout the system, and can cause cloudy water, poor heater operations, and increased wear and tear on your equipment. Approximately every 3-5 years the old sand will need to be removed and new sand added. Under some circumstances the sand must be changed every year (painted pools, and some fiberglass pool surfaces plug up the sand very quickly)
Drawbacks for sand filters include:
Longer filtration times are required.
Filtration efficiency is 40-50 microns.
More specialty chemicals are required to keep the pool clean and clear.
Uses high volumes of water for backwashing.
Filter maintenance is often neglected since sand filters are sometimes sold as “maintenance free”.
Cartridge filters come in various sizes and shapes. The filter canisters or tanks are made of fiberglass or plastic composite. There are usually four cartridge elements inside this filter. The cartridge elements are cylindrical, and made of a paper cloth-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 filters; its micron rating is about 20 microns. This filter is cleaned periodically depending on pressure by removing the elements from the canister and hosing it off using your water hose.
Drawbacks for the cartridge filter include:
Most cartridge filters are undersized for the pool they are on.
The manually disassembling for filter cleaning is tedious and difficult for some people.
The filter elements need replacement (oils and impurity can plug and even crush the element)
Since the water is never removed through backwashing the pool hardness and total dissolved solids become extremely high. (Your pool needs to be drained more often)
DIATOMACEOUS EARTH (DE) FILTERS:
D.E. filters are made of fiberglass or plastic composite. 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 for 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 either a sand or cartridge filter, and therefore provides better water clarity. The filter is usually backwashed every 3-5 months by reversing the flow of the water witch removes the dirt and the D.E. out the backwash line. 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.
Drawbacks for the D.E. filter include:
Each time you backwash or clean a D.E. filter you need to re-add D.E. powder to the skimmer.
The filter should be disassembled and cleaned twice per year. The manually disassembling for filter cleaning is tedious and difficult for some people.
The grid elements need replacement (oils and impurity can plug and even crush the element)