PoolsOnly.com Filter Guide

Swimming Pool-Spa Filter Types: Probably the most important decision when selecting a pool or spa filter is that it's sized correctly for your pool/spa. You should always choose the largest filter you can afford (bigger really is better when it comes to filters) because inadequate filtration will cost you time, aggravation and money.

Diatomaceous Earth (DE) Filter
Diatomaceous Earth Filter, most commonly known as DE filter, is one of the most efficient pool-spa filters available. It can catch particles in the range of 3 - 5 microns, much too small to be seen with the naked eye. Pool-spa DE filters are made of a "filter element" and a tank. The filter element consists of a very fine fabric grid, coated with the actual filter media called "DE". DE is nothing but the crushed fossilized remains of Diatoms. Diatoms are microscopic sized, hard shelled creatures covered with sharp spines. Diatoms are found in both, marine as well as fresh water environments. To the naked eye, DE looks like very fine white powder, under the microscope it resembles a sponge.
The DE filter user adds the DE to the skimmer, the DE is then trapped in the grid inside the DE filter tank. The DE now covers the filter grid, allowing the pool-spa water to go through, but trapping particles in suspension in the water. As more and more particles get trapped in the filter element, the water pressure rises, while the flow rate decreases. You need to backwash the filter to keep its efficiency, and the quality of the pool-spa water being filtered. This is usually done when the pressure gage reaches around 8 to 10 lbs above the clean water pressure. When you backwash the DE filter, the water flows through the filter in reverse, washing away the particles trapped in the filter element, along with some of the DE powder. Note that some municipalities regulate closely the amount of DE being disposed. DE filters should be thoroughly cleaned at least once a year. If you use soft swim, or baquacil products (biguanides) in your pool-spa, you need to clean the DE filter twice a year to prevent it from clogging up. The filtration capacity of a pool-spa DE filter is proportional to the square footage of the active surface element. If you are looking for a specific filter and you can't find it on our web site, please contact us and we'll try to find it for you.

Sand Filter
As the name implies, the filtering media in sand filters really is sand. But it's not just any sand -- it is #20 silica sand, an important fact to remember when it comes time to change your filter's sand. Pool and spa sand filters can trap particles in the range of 30 to 50 microns. The sand grains, which make up the filter media, have rough edges; these rough edges is what allows the sand grains to trap particles in suspension in the water, as it rushes around the sand grains. Given enough time, the sand grains turn less rough, and more rounded, loosing in this way their ability to trap particles. At this point, the sand should be changed, this is roughly about every 5 to 10 years, depending on the use. There are new products that can be used instead of sand, these products increase the efficiency of the sand filter, to the point where they could compete with the DE filters, in terms of the size of particles that it can trap. As a general rule, pool-spa sand filters should be backwashed when the pressure gage shows pressures about 8 to 10 lbs over the clean pressure reading. the backwash process involves changing the flow of the water, such that the trapped particles are washed out of the sand grains, and the filter.

Cartridge Filters
Such filters typically hold one to four cartridges, each being made of a fine mesh pleated material. Water flows through the filter media where the particles get trapped. Cartridge filters can trap particles down to 25 microns. When the trapped particles accumulate on the surface of the cartridge (and the pressure gauge shows pressures about 8 to 10 lbs over the clean reading) it's time to pull out the cartridge and wash it, as opposed to backwashing like in DE or sand filters. However, every time the filter is washed, its cleaning ability and therefore life, is reduced. As with DE filters, the filtering capacity of a cartridge filter is a function of its surface area -- the size and number of pleats and folds in the cartridge. Cartridges should be changed every 1 to 3 years, depending on use and dirtload.

Types of Backwash Filter Valves

1 - The Rotary Valve
2 - The Piston Valve

In the process of filtering your pool or spa water, particles suspended in the water get trapped in the filter media. As more and more particles get trapped, the efficiency of the filter diminishes and the quality of your pool or spa water is compromised. The purpose of the backwash valve is to allow the user to redirect the flow of water through the filter in such a way that trapped particles can be flushed out of the filter,via the waste pipe. Both types of valves have mechanisms inside that allow them to properly redirect the flow of water based on the position selected by the user. The rotary valve has a lever that the user rotates to the proper position to select the desired filter function. The piston valve has a piston which is raised or lowered to select the desired filter function. There is also another type of valve called the multiport valve; this valve looks and behaves very much like a rotary valve, therefore, for our purposes, we will treat it the same. The multiport valve has several positions, here is a brief description of those positions.

Backwash: The position to use to flush out, particles trapped by the filter. Make sure all valves are open, and the waste line free of kinks, or any other obstruction.

Closed: This position is used mostly to work on the swimming pool equipment. When in this position, the flow of water from the pool is blocked. NEVER turn on the pump when the valve is in this position.

Filter: This is the "normal" position of the valve, and where it should be most of the time. In this position the pool-spa water is circulated through the system in such way that it is purified by the filter.

Recirculate: In this position the filter is off line, in other words, the water is recirculating, but the filter is bypassed, not filtering.

Rinse: Used after you backwash the filter, it must be rinsed to keep debris from going back into the swimming pool-spa water.

Waste/Drain: In this position, the water suctioned from the pool is sent out straight to the waste line, it never returns to the swimming pool.

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Pool Filter Backwashing. What is it?
Backwashing a pool filter involves reversing the flow of water through the filter as to wash away any particles trapped on the filter media.
Pool-spa water normally flows from the swimming pool-spa, through the filter, where the filter media traps particles in suspension. The, now clean water, is directed back into the swimming pool or spa. As more and more water flows through the filter, more and more particles get trapped in the filter media. Eventually the number of trapped particles is large enough that the flow of water is reduced, causing the pressure to rise, and the quality of the swimming pool or spa water to suffer; it is time to backwash. In the backwash mode, water flows from the pool through the filter media, but this time in the reverse direction, flushing out the trapped particles, or at least most of them. This "dirty" water is not thrown back into the pool, instead it is redirected to the waste line.

How to backwash (DE filter):
Make sure you follow the manufacturer's directions when handling a DE filter. DE filters should be backwashed when the pressure gage reads 8 to 10 lbs above the clean reading The clean reading is the pressure reading after the filter has been thoroughly cleaned- backwashed. Pay particular attention to the amount of DE that you add after a backwash. Should you add too little, the grid will quickly get clogged with dirt, bad news!!. Should you add too much, it won't take long either for the filter to get clogged up again. That said, too much is always better than too little. As stated before, make sure you follow the manufacturer's instructions, but as a general guideline, this is the procedure used to backwash a DE filter equipped with a rotary valve:
  1. Turn off pump
  2. Push down on the valve handle, and rotate to BACKWASH, make sure that the waste line is unobstructed
  3. Open air bleeder assembly on filter
  4. Turn on pump
  5. Keep an eye on the pressure gage to spot any abnormal pressure which will indicate a problem. If there is a problem, turn off pump immediately, find and fix the problem.
  6. Run pump until water runs clear.
  7. Turn pump off.
  8. Push down on valve lever and turn to RINSE, let run for 5 to 20 seconds.
     Repeat the BACKWASH/RINSE procedure 2 or 3 times.
  9. Turn off pump and turn valve to the FILTER position.
  10. Turn on pump
  11. Add DE as required by your filter manufacturer, usually around 1 lb/10 feet square of filter area.

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How to backwash (sand filter):
Make sure you follow the manufacturer's instructions when handling your sand filter. Pool-spa sand filters should be backwashed when the pressure gage reads 8 to 10 lbs above the clean reading The clean reading is the pressure reading after the filter has been thoroughly cleaned/ backwashed. As stated before, make sure you follow the manufacturer's instructions, but as a general guideline, this is the procedure used to backwash a sand filter equipped with a rotary valve:

  1. Turn off pump
  2. Push down on the handle, and rotate to BACKWASH, make sure that the waste line is unobstructed.
  3. Turn on pump
  4. Keep an eye on the pressure gage to spot any abnormal pressure which will indicate a problem. If there is a problem, turn off pump immediately, find and fix the problem.
  5. Run pump until water runs clear.
  6. Turn pump motor off.
  7. Push down on valve lever and turn to RINSE, let run for 15 to 30 seconds.
     Repeat the BACKWASH/RINSE procedure 2 or 3 times.
  8. Turn off pump and turn valve to the FILTER position.
  9. Turn on pump

How to clean your cartridge filter:
Cartridge filters are not backwashed, instead, they are taken out of the tank and hosed clean; usually with a pressure washer. Cartridge filters should be cleaned when the pressure gage reads 8 to 10 lbs above the clean reading. The clean reading is the pressure reading after the filter has been thoroughly cleaned. This is the general procedure used to clean a Cartridge filter.

  1. Turn off pump
  2. Remove filter lid
  3. Hose filter thoroughly
  4. Replace filter in tank
  5. Replace filter lid.
  6. Turn on pump