History of spa filters
||This article is written like a personal reflection or opinion essay rather than an encyclopedic description of the subject. (June 2010)|
Traditionally, the filter in a pool or spa is the hardest piece of equipment in the water care system. They work continuously to keep debris and sediments from the water. So when selecting a system – you want to have all the facts to ensure that your selection is durable and not fraught with flaws that can keep you from enjoying your spa. So here are the current technologies that dominate the market today with a narrative that walks you through how they work. Then we walk through a simple guide on how to take care of your system to ensure its longevity.
Sand filters have been around since the 17th century. Around 1627, Sir Francis Bacon compiled 10 experiments in "A Natural History of Ten Centuries". He hypothesized that water could be filtered through sand purifying seawater. This hypothesis was incorrect, but did spur a wave of interest in the discipline.
As the name suggests, the main filter medium is sand. Sand filters look like large balls and they can hold hundreds of pounds of sterile sand. Essentially, water flows in through 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, this same principle is seen in some simple fish tanks using their bubbler to draw the water through the gravel at the base of the tank. Sand filters are efficient enough to keep just about any pool clean, removing particles as small as 20 to 25 micrometres.
As dirt builds up it acts as a filter aid by reducing the porosity of the sand bed thus trapping smaller particle sizes, but will eventually blind the filter and require backwashing where the flow of water is reversed back through the filter to purge the system. The disadvantage, however, is that the backwashed water is simply wasted. A typical backwashing session can waste a few hundred gallons of water – water that must be replaced to replenish the pool level. This process may need to be performed as much as once a week during the swimming season, depending on the size of the filter. This might be an important consideration where the accumulated cost of purged chemicals and water is concerned.
|This section does not cite any references or sources. (November 2012)|
Cartridge filter technology was invented in the mid-1960s. Despite the system’s availability for around half a decade, it has only taken precedence over the other filtration technologies relatively recently.
First appearing in oil filter configurations, Cartridge filters have larger surface areas compared to sand filters. This enables cartridge filters to operate for longer periods, as obstructions occur less with bigger filter surfaces. Cartridge filter systems also permit better water flow – 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. Cartridge filters require cleaning around four to eight times a year. The filter will primarily catch larger debris while the cartridge is clean. Once the filter’s pores become clogged with larger particles, the buildup will allow the filter to trap smaller debris.
The filters are actually made of polyester or some 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 unwanted dirt or debris in the water. The fabric catches and holds the impurities until you clean or replace the filter. 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 (Remay being the dominant brand). Cartridges are high efficiency depth style filters constructed of polypropylene. Constructed of polypropylene, 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. A grain of table salt is about 90 micrometres; anything below about 35 micrometres is invisible to the naked eye. It is important to remember that with any filter a small amount of dirt actually aids the filtering process. 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. Some families will find it 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 in top shape.
There are more than 500 shapes and sizes of spa filter cartridges in use today. Most major spa brands have designed their own yet all of them are available from aftermarket sources.
Diatomaceous earth filters
|This section does not cite any references or sources. (November 2012)|
It's hard to comprehend that the fossilized remains of single-celled plants that lived 15,000 years back may be of use to us in today's modern world, but scientists have come up with a method to utilize the Diatomaceous Earth ( D.E. ) they made by dying in the sea areas of their world. These remains of minuscule plants are called diatoms, and together they create a white, unscented powder which has become quite helpful to mankind.
DE Filters, these products can filter out dirt as small as 3 to 5 micrometres. If you opened the tank of a DE filter it would look somewhat similar to a cartridge filter.
DE Filters are usually the most expensive type, and they get your pool water cleaner than the other filters. But the necessary maintenance can be a drawback for some homeowners. Most manufactures call for backwashing to clean the filter. In backwashing, the system reverses the flow of water. The clean water cleanses the filter. The dirty water is drained from the system.
John Doulton founded his first pottery in 1815 at Lambeth, England on the banks of the Thames river. The main products of the original company were ceramic busts, figurines, canning jars and tableware. Influenced by the unrelenting progress of the Industrial Revolution, Doulton placed equal emphasis on industrial applications for ceramic technology. As early as 1827, this fine china manufacturer was in the water treatment business, using various earth and clay materials in the first Doulton water filters.
In 1835, Queen Victoria recognized the present health dangers in her drinking water and commissioned Doulton to produce a water filter for the Royal household. Doulton created a gravity fed stoneware filter that combined the technology of a ceramic filter with the artistry of a hand crafted pottery water container. In consideration of her pleasure with the new device, Queen Victoria bestowed upon Doulton the right to embellish each of its units with the ROYAL CREST.
John Doulton's son, Henry Doulton, introduced the Doulton Manganous Carbon water filter in 1862, the same year that Louis Pasteur's experiments with bacteria conclusively exploded the myth of Spontaneous Generation. This more advanced understanding of bacteria made it possible to direct Research and Development efforts to the creation of a porous ceramic capable of filtering our these tiny organisms.
By 1901, King Edward knighted Henry Doulton and honored the company by authorizing it to use the word ROYAL in reference to its products. In 1906, Doulton introduced a filter that proved to be equal to the one Louis Pasteur had developed in France. It was rapidly adopted by hospitals, laboratories and for use in domestic water filtration throughout the world. The popularity and effectiveness of even the early 20th century designs has resulted in their continued use in Africa and the Middle East. The range and efficiency of Doulton domestic water filters has been widely extended over the years to meet the demands of increasingly sophisticated uses.
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. In developing countries, they are manufactured locally—sometimes as a self-financed micro-enterprise. These devices are typically shaped like a flowerpot or a bowl and are impregnated with tiny, colloidal silver particles as a disinfectant and to prevent bacterial growth in the filter. The filter sits inside a 20- to 30-liter plastic or ceramic receptacle with a spigot.
Laboratory testing has shown that, if designed and produced correctly, these devices can remove or inactivate almost all bacteria and protozoan parasites. Its effectiveness against viruses is unknown.
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 liters per hour.
Dr. David Manz developed the household biosand filter in the 1990s at the University of Calgary, Canada. Dr Manz has trained many organizations on the design, construction, installation, operation and maintenance of the biosand filter. He also co-founded CAWST in 2001 to provide the professional services needed for the humanitarian distribution of the filter in developing countries. As of June 2009, CAWST estimates that over 200,000 biosand filters have been implemented in more than 70 countries around the world.
Slow sand systems have recently been adapted for point-of-use systems, especially in developing countries. In this context they are generally known as “biosand” filters. Most commonly, a biosand filter takes the form of a container a little less than a meter tall and perhaps 30 cm in width and depth, filled with sand. The biologically active layer, which takes a week or two to fully develop, is maintained by keeping the water level above the top of the sand. As with slow sand filters, this bioactive layer helps to filter, adsorb, destroy, or inactivate pathogens. A porous plate is usually located above the sand to prevent disturbance to the bioactive layer when water is added. Users simply pour water into the top of the apparatus, and collect treated water from the outlet.
In laboratory and field testing, biosand filters have removed nearly all protozoa, and most bacteria. Their performance with viruses is not well established. The apparatus can be built using concrete—a commonly available and relatively inexpensive material. Maintenance is fairly simple, usually consisting of agitating the upper surface of the sand once a month or so and manually collecting the suspended material. The cost of upkeep is quite low, since there are few or no parts to replace.
Spa Filter Care
||This article contains instructions, advice, or how-to content. (June 2010)|
Filter manufactures recommend cleaning spa filters on a monthly basis to avoid reduced water flow. Clogged filters are reported to be the leading cause for repair service calls and spa pump failure. Consult the spa owner's manual for correct filtering cycles, the most common of which is 4 hours per day. Many spas built after 2000 have programmed filter cycles built into the electronic control systems.
It is also recommend filters be replaced 12 to 18 months regardless of appearance due to material breakdown even if not visible. Filter manufactures also recommend showering before using your spa to reduce contaminants that can clog the filter such as: hair spray, mousse or styling gel, deodorant or anti-perspirant, sun tan lotion, excess sweat and skin creams. It also important to regularly check and maintain the proper chemical balance in the water to increase the life of the spa filter.
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- Constructed of polypropylene http://www.membrane-solutions.com/pleated_cartridge_filters.htm
- "Royal Doulton water purifiers. History of Doulton water filters". Doultonusa.com. Retrieved 2010-09-15.
- "Safe Drinking Water is Essential - Filtration Systems - Technologies". Drinking-water.org. 2007-09-01. Retrieved 2010-09-15.
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