Spa filters work continuously to keep debris and sediments from the water in a spa pool.
Cartridge filters
Cartridge filter technology was invented in the mid-1960s, cartridge filters have a large surface areas enabling them to operate for long periods. Cartridge filter systems also permit better water flow â€" thus, placing less strain on the filter pump. These types of filters are also easiest to clean by using a flow of high-pressure water from a hose. The filters are made of polyester or other material that can provide a superfine filtering surface. The pleats are the key to the filter's operation. The tight pleats, or folds, allow for a large amount of material to be used in a small container. The more material used, the larger the surface area available to capture dirt or debris from the water. The fabric catches and holds the impurities until the filter can be cleaned or replaced. There 3 parts to a cartridge filter construction,end caps (made of plastic) core structure to provide strength (most often PVC) and the pleated media (most often polyester with a continuously graded fixed pore structure, these cartridges provide pre- and final filtration within the same cartridge resulting in lower overall filtration and disposal cost.
Two methods are used in spas with respect to cartridge filters, pressurized canisters,in which the spa filter is not visible when in use, and secondly flow through systems, which are visible when in use and often the spa has 1-5 filter cartridges in this design. Flow through filter system in spas and hot tubs are the preferred method of design today for all major hot tub brands.
The cartridge can filter out anything down to about 5 to 10 micrometres in size. In most areas cartridge filters are less expensive than diatomaceous earth filters but cost more than sand filters. However cartridge filters are more popular because of the minimal maintenance involved. In some cases it may be sufficient to simply hose off the cartridge filter a few times during swimming season to keep them working properly. Others may need to soak the filters in detergent or replace them. In any case, maintenance takes only a few minutes to the filtration system operational.
There are more than 500 shapes and sizes of spa filter cartridges in use today.
Diatomaceous earth filters
The fossilised remains of diatoms are mined as Diatomaceous earth; a white, unscented powder widely used in industrial filtration applications and also available for spa pool use in cartridge format.
Ceramic filtration
Ceramic filters have been used for water treatment for several centuries. While they are being marketed for centralized water treatment systems, most ceramic filters are now being manufactured for point of use applications.
Cleaning and maintenance of the filter is critical; so like other low-cost point of use systems, it is best combined with an educational program about safe storage, filter cleaning, and other recommended practices. The advantages of ceramic filters are their ease of use, long life (if not broken), and fairly low cost. Disadvantages include possible recontamination of stored water since there is no chlorine residual and a relatively low flow rate - typically one to two litres per hour.
Sand filtration
These filters use sand as the filtering medium. Sand filters look like large balls and they hold hundred of pounds of sterile sand. Water flows into the top of the filter housing and makes its way down through the sand bed where the sharp edges of the sand catch the particulates. On a micron-to-micron comparison, sand filters remove the least amount of dirt â€" particles as small as 20 to 25 microns. However, sand filters certainly are efficient enough to keep just about any pool clean.
To keep a sand filter working, depending on the size of the filter you must clean it as often as once a week. Maintenance means backwashing where the flow of clean water is reversed back into the filter. The problem with this, however, is that backwashed water is simply wasted. A typical backwashing session can waste a few hundred gallons of water â€" water that must be replaced.
See also
- Hot tub
- History of water filters
References
