The oldest and most popular method of filtration is the sand filter. The high-rate sand filter was introduced more than thirty years ago and the only type of sand filter currently used for residential pools. They come in all sizes and shapes.
All sand filters share a couple of features, when in the filtration mode, water always flows from the top down and they all have some sort of lateral or underdrain designed with slots or holes to hold back sand while allowing the clean, water to pass through.
Outward appearance of filters and internal assemblies may vary, but, basically all sand filters operate the same way. Sand is added to the filter through a top valve or domed opening in the tank or by removing a cover. Vertical standpipes must be covered by a protective cap (a baggie or a coffee can will do) to keep from getting sand into the internal plumbing.The sand should be poured gently into the filter, being sure not to damage the laterals or underdrain. A good practice is to add enough water to cover the laterals or underdrain , because this will cushion the falling sand. On top-mount filters, be sure the lateral assembly is positioned properly into the center of the tank before pouring in the sand. Various guides are used to insure that the assembly is properly set, because improper seating of the vertical standpipe will prevent the valve from seating properly and may require that you remove all of the sand to reset it. Holding the top of the standpipe down while pouring the sand will prevent it from dislodging.
Once the proper amount of sand is added, the protective cap should be removed and the valve or dome mounted in place. Some valves thread into the top of the tank, others are held by clamp. All valves use some sort of O-ring as a seal. A liberal amount of O-ring lubricant should be applied to both the O-ring and the external threads to allow the valve to seat properly. On flange mount valves, this lubrication will allow adjustment once the clamp is semi-tightened. Be sure the lubricant is non-aggressive to plastic or rubber.
Sand filters use a special filter sand, normally .45 mm to .55, which is also known as pool grade #20 silica sand. The special sand has sharp edges that serve to separate particles, allowing filtration to take place. once the proper amount of sand has been added to the filter, it functions as the permanent dirt removing medium. Water from the pool, containing suspended dirt particles, is pumped through the piping system and is directed automatically by a filter control valve to the top of the tank. As the pool water is pumped down through the filter tank through the control valve and back to the pool through the piping system. his entire sequence is continuous and automatic and provide for total recirculation of the pool water. After a period of time, the accumulated dirt in the filter causes a resistance to flow, and the flow diminishes. This simply means that it is time to backwash (clean) the filter. With the control valve in the backwash position, the water flow is reversed through the filter so that it is directed to the bottom of the tank and up through the sand, thus flushing the previously trapped dirt and debris out the waste line. Once the filter is backwashed , the control valve is re-sequenced manually to -rinse- and then to -filter- to resume normal filtering. To prevent unnecessary strain on pipes and valves, always shut off the pump strainer and skimmer baskets regularly. Most Manufacturers require that new filters be started with the valve in "backwash" position for approximately two minutes. This is to remove any impurities or fine sand particles which normally exist in any new change of sand. The most common type of valve in use today is the 6-way multiport valve, which is manufactured by a number of companies. The one produced by Hayward is the most widely used and is the Vari-flo TM series. Following are the various positions and their functions.
FILTER- This is the valve position for normal filtration and is also the one used for normal vacuuming.
BACKWASH- Used for cleaning when the filter pressure gauge rises 6 to 8 pounds above the normal clean pressure, stop the pump and change the valve position to backwash . Start pump and backwash until water runs clear. This takes two minutes or less depending on dirt accumulation.
RINSE- After backwashing, with pump off, set valve to Rinse. Start pump and operate 30 seconds to 1 minute. This assures that all dirty water from backwashing is rinsed of of the filter to waste, preventing possible return to the pool. Stop pump and set valve to filter, and start pump for normal filtering.
WASTE- Used to bypass filter for draining or lowering the water level and for vacuuming heavy debris directly to waste.
RECIRCULATE- Water is circulated through the plumbing and valve, but bypasses the filter tank.
CLOSED- Shuts off flow from pump to filter. Do not shut off pump with running.


  • Filter in need of backwashing
  • Check skimmer and pump strainer baskets for debris
  • Check for clogged or restricted suction or return line
  • Check for a leak in suction lines. Any bubbles back to the pool confirm that the leak is on suction side of the pump
  • Laterals or underdrain may be clogged
  • Algae Superchlorinate to 30 ppm
  • Using Calcium based chemicals
  • Surface of sand bed crusted or caked. Remove 1" old the sand bed
  • An excess of oils and dirt cause mud balls in the sand. (Replace sand)
  • Filter not being run long enough
  • Chemicals out of balance
  • Valve not in filter position
  • Pump could be hooked up wrong.

If water doesn't clear after running filter 24 hours, you probably have contaminants too fine for the sand filter. Since sand filters only filter to about 30 microns you will need to provide something that will help filter finer materials. We recommend SPARKLE SANDAID.
Do Not Backwash too often. Wait until the pressure reading is 6-8 pounds above normal. Sand should be changed at least every other year.