Backwashing Sand and DE Swimming Pool Filters, How to Operate a Pool Filter

by Pool Builders on 08-29-2007 in Articles

Filtration is one of the most important factors in the circulation system of your pool to keeping it clean. There are three types of swimming pool filters available for pool owners. Sand filters, Cartridge filters and DE Filters. It is important to know which filter you have on your pool and how to maintain and operate it. Each of these pool filters have their own advantages and disadvantages. With any pool filter you choose it is important to keep the proper sizing in mind. Proper sizing refers to the pool volume and the size of pool pump.

Sand Filters:

Sand filters work by pushing water through a bed of sand and into laterals. Sand filters generally have the advantage of being reliable and simple to operate. Sand filters are capable of continually filtering water with out shutting off the pump for days on end. As long as proper water balance is maintained along with regular cleaning cycles the sand inside the filter well be good for up to 10 years. If you are having a problem keeping your water clean and clear only, change the sand as a last resort, other problems in the pool chemistry are probably the cause.

Backwashing Your Sand Filter:

When the filter becomes dirty pressure will build up, and you can see this on the pressure gauge. When the pressure gauge reads approximately 5 to 7 PSI above the normal operating pressure you know that the filter is dirty and it is time to backwash. Backwashing is an easy process. Backing washing is done by first turning the pump OFF. Note: Always turn the pump off while moving the filter multi port valve. Once the pump is off, turn the multi-port valve on the filter from the 'filter' position to the 'backwash' position. Once the filter is in the backwash position turn the pump back on. The water is then reversed through the sand by the pump. The dirty water gets sent out the waste line (usually into the yard). High concentrations of chlorine can kill grass so it is important to know what the chlorine level is in the pool while backwashing. A 1 to 2 ppm range should be safe it avoid killing the grass. Once the water coming out the waste line is turns from dirty to clean (may take up to 3 min.) turn the pump back off. Once the pump is off move the multi-port valve back from the backwash position to the rinse position. Turn the pump back on and let it run for about 20 seconds. Then turn the pump back off and move it to the filter position.

Lets recap the backwashing steps:

Filter Position-> Pump Off -> Backwash Position-> Pump On for 2 min. ->Pump Off -> Rinse Position-> Pump On for 30 Seconds -> Pump Off -> Filter Position

Diatomaceous earth filters:

Diatomaceous earth filters use grids inside coated with diatomaceous earth or DE for filtration. DE filters have the advantage of filtering to the finest particles or microns. However, they have been considered the most hassle to operate. For proper operation of a DE filter it must be turned off for about 4 hours everyday. This is to allow the DE to drop and be recoated when the pump comes back on.

Back washing a DE filter:

Like sand filters they also require backwashing when the pressure rises to about 6 pound above the normal operating pressure. After backingwashing you must recoat the filter grids with new DE. This is done by feeding DE through the skimmer so it gets pumped into the filter tank. DE is a white powder substance that must be purchased at pool store. About twice a year DE filters should be taken apart and the grids cleaned. Most DE filters have a multi port valve on them used for backwashing. Backwashing is an easy process. Backingwashing is done by first turning the pump OFF. Note: Always turn the pump off while moving the filter valve. Once the pump is off, turn the multi-port valve on the filter from the 'filter' position to the 'backwash' position. Once the filter is in the backwash position turn the pump back on. The water is then reversed through the grids by the pump. The dirty water with old DE gets wasted out the waste line (usually into the yard). High concentrations of chlorine can kill grass so it is important to know that the chlorine level in the pool is low while backwashing. Once the water coming out the waste line turns from dirty to clean (may take up to 3 min.) turn the pump back off. Once the pump is off move the multi-port valve back from the backwash position to the rinse position. Turn the pump back on and let it run for about 20 seconds. Then turn the pump back off and move it to the filter position. Now its time to recharge the DE in the tank. Refer to the label on the filter for the proper about of DE to be added, it should say how many pounds are required for a recharge. Turn the pump back on and go over to the pool skimmer. Add the recommended number of pounds to the skimmer slowly. It is best to make a slurry in a bucket then slowly poor it into the skimmer so avoid clogging. At this point it is a good idea to take a look at the return line in the pool to be sure that the DE is being caught in the filter. If you have white powder spraying out the return jets in the pool then you know you have a problem in you grids or the valve is set in the wrong position.

Lets recap the backwashing steps for a DE filter:

Filter Position-> Pump Off -> Backwash Position-> Pump On for 2 min. ->Pump Off -> Rinse Position-> Pump On for 30 Seconds -> Pump Off -> Filter Position-> Pump On->Recharge filter with DE from skimmer

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