What is a swimming pool filter?
Swimming pools are subject to constant contamination from foreign matter brought in by swimmers, wind and articles used in and around the pool. The job of swimming pool products like pool filters is to remove the tiny dirt particles that make the water cloudy. Water clarity is important for appearance, hygiene and safety. Pool water filters are the hardest working piece of pool equipment. Swimming pool filters work round-the-clock to filter impurities so you can enjoy pure water. You'll want a durable swimming pool filter that will remove even the smallest debris and sediments from your water. Swimming pool products like pool filters are universal in pool systems, linked to the circulation system along with the motors, swimming pool heaters and pumps. As water pumps through the circulation system of a swimming pool, impurities are strained by a water filter. The swimming pool filter itself has no moving parts and is made of simple components. As with most swimming pool equipment, smaller swimming pool filters can accommodate an above ground pool, but inground pools need something larger.
What types of pool water filters are there?
Sand filters
Sand filtration has been around longest and is still most common. With this method, water flows from the top to the bottom of the swimming pool filter, after which a lateral system holds the sand back while allowing the water to pass through. This system is also used to return the water to the pool after it has been cleaned. Sand filters are large tanks that hold big amounts of pool sand. Sand filters use a special type of sand to clean the water, generally a no. 20 silica sand with grains which are approximately 40-55 millimetres and have sharp edges to separate unwanted particles and allow them to be filtered out. These pool water filters operate on the basis of depth filtration, whereby dirt is driven through the filter sand and collects in the spaces between the grains. Sand filters can remove dirt particles down to about 20-25 microns in size. Initially, the clean sand bed traps the largest dirt particles; then, as more are collected in the bed, the swimming pool filter traps increasingly smaller particles until the water is clean. In order to clean them (they need cleaning about once a week), sand filters are cleaned by backwashing-reversing the flow of water from the swimming pool filter into a ‘waste’ line which flushes out the debris, achieved by multi-port valve which is either side- or top-mounted. The fact that sand filters can only remove particles up to a certain size makes it a less effective method for cleaning pool water, although it will still get the job done. Maintenance can be tedious and sand filters are perhaps the least expensive of available swimming pool filters.
Diatomaceous earth filters (DE)
The newest discovery in pool water filtration is diatomaceous earth, or D.E. This has become the most effective method of filtration as it has the capacity to remove even smaller particles than cartridge filters. Diatomaceous earth is a powder made of billions and billions of fossilized plankton skeletons. D.E. filters have an internal element that must be pre-coated with D.E., creating a filter cake that traps the dirt particles. It works very well to catch and hold dirt. They are the most expensive type of swimming pool filters, and they get the water cleaner than other types of pool water filters. Clear water is able to flow through the powder, but particles as small as one to three microns will become trapped on the first pass through the water filter. Maintenance can be demanding, however. Most of them require back washing, and this isn't always enough to get them clean. You may have to remove the grids and discard the used diatomaceous earth. This can be a pain since some towns classify it as hazardous waste, so you cannot simply throw it away.
Cartridge Filters
The next method of filtration to be developed is cartridge filtration. Cartridge technology has been around for a relatively long time, but people have only recently realized its usefulness for swimming pools. This method is superior to sand, as it has twice the amount of filtration capacity of its older cousin and can remove smaller particles. A cartridge filter is a tank that holds 3 or 4 cylindrical cartridges. Each cartridge is made up of some fabric like polyester that catches the tiny particles of dirt and holds them until you clean the swimming pool filter. Here, water flows through the cartridge element, where dirt is screened out. As with sand filters, when the cartridge element is clean it traps the largest particles, accumulating increasingly smaller ones as the pores of the element become clogged. Cartridge filters can handle dirt as small as 5-10 microns in size (anything smaller than 35 microns is impossible to see with the naked eye). Cartridge filters are usually less expensive than diatomaceous earth filters but cost more than sand filters. Cartridge filters require very little maintenance. Cartridge filters need regular cleaning, but this can be done easily by removing the element, soaking it in Tri-Sodium-Phosphate, and rinsing it with a hose. Alternatively, spraying it with a high pressure garden hose will also do the trick. You can sometimes get away with just hosing off the cartridges a few times during the swim season. At the worst, you replace the cartridge (they are relatively inexpensive).
How does the swimming pool filter influence the swimming pool heater?
The most common swimming pool heater ailment to a swimming pool heater not working is that the pool water filter is too dirty, not allowing enough water flow to go through and turn on the swimming pool heater. A polluted pool water filter can stop the swimming pool heater. Because at first the swimming pool water runs through the swimming pool water filter and then it is pushed through the swimming pool heater. If the water flow through the swimming pool filter is not strong enough, for example there is an accumulation of debris or dirt in the water filter, the pool heater cannot get enough water flow and the heater will stop. To fix this problem, you need to chemically clean your water filter. To prevent such a situation it is recommended to clean the swimming pool filter in constant periods. Chlorine generators, gas-fired swimming pool heaters, heat pumps, solar systems all require certain gallon per minute rates and each have different levels of restriction or head loss for those flow rates. For swimming pool heaters a minimum flow rate of 5000 l/min is required. When designing a complex pool project it is advisable to have manufacturers' flow and pressure drop tables to insure balanced flow for elements of the pool.
