SINCE 1958

San Rafael Ca, 94903
3769 Redwood Highway

Herb's Filter Featured Article



It is necessary to backwash your sand filter at least once a month in season or every few months in the off season. They have a permanent sand “bed” so backwashing only results in losing water. Sand filters should be cleaned every few months by adding Filter Magic or another filter cleaner to the water. This will chemically clean the sand and help to improve water clarity. Sand itself should be replaced every 3-5 years. A sand filter is reliable and fairly simple to operate; unfortunately it only filters down to 25 microns without the use of a clarifier product of some sort. Because backwashing the pool lowers the water level it is recommended to turn on your water fill line when doing so. This will prevent the water level from dropping below the level of the skimmers.
1. Turn the pump off.
2. Empty the skimmers and the pump pot basket
3. Turn pump on and bleed any air out of the system
4. Turn the pump off
5. Most sand filters have either a push-pull valve or a multiport valve. Change the position from filter to backwash
6. Turn the pump on
7. Allow the backwash to run for 3 to 4 minutes or until the water runs clear through the sight glass.
8. Turn the pump off
9. Switch the valves from backwash to filter.
10. Turn on the pump and bleed any air out of the system


Cartridge filters should be cleaned every several months or when filter pressure reaches 10 PSI above the initial clean cartridge starting pressure. They will filter down to 10 microns of debris when in good condition. Cartridges should be replaced every 3-5 years as the fabric becomes more porous and clogged of organcics etc. If the cartridge is damaged, the pleats are ripped, the plastic caps are broken, the bands are broken or the pleats are blown out, then it is time to replace the cartridge. Here is how to clean them:
1. Turn off the pool equipment.
2. Bleed the air from the filter using the air relief valve.
3. Open the filter and remove the cartridges.
4. Spray the cartridges down with water prior to adding a filter cleaning agent
5. Spray the cartridges with a filter cleaning agent such as Kleen It or Filter Magic.
6. Allow the cartridges to soak for 10-20 minutes.
Hose the cartridges down with the garden hose to remove oils, debris and the filter cleaning agent. The retail stores carry a attachment for the water hose that is perfect for this method and cuts the rinsing time down in half.
7. Replace the cartridges in the filter
8. Turn pool equipment on and bleed any air out of the system.


It is necessary to backwash your D.E. filter once a month or whenever the filter pressure exceeds 8 to 10 PSI over starting pressure. A D.E. filter is the best of the 3 in terms of filtration and cleaning. It can filter all the way down to a 2-3 micron piece of debris. Twice a year it is necessary to take the D.E. filter apart and chemically clean the grids. While backwashing, the pool will lose water so it is necessary to make sure that the water level stays about halfway up the skimmer opening. It may be necessary to run your fill line or turn your water hose on to keep the water at a safe level.
1. Turn pool equipment off
2. Empty out the pump pot and skimmer baskets
3. Close the pump pot and turn on the pool equipment
4. Bleed any excess air out of the system
5. Turn system off. Push the multiport valve down and turn it to the backwash position. Always turn the valve in one direction only.
6. Turn system on
7. Backwash filter for 2 minutes or until the sight glass water runs clear
8. Turn system off
9. Turn the multiport valve to the rinse position. Always turn the valve in one direction only.
10. Turn system on for 15 to 30 seconds
11. Turn system off
12. Repeat steps 5 through 11 at least 1 more time. Always finish the cycle in the backwash position.
13. Turn the system off
14. Change the multiport valve from backwash to filter. Always turn the valve in one direction only.
15. Turn the system on and bleed any air out of the system
16. Add D.E. to the skimmer closest to the equipment. The amount of D.E. is determined by the filter size. (See chart below)
17. After adding the D.E. check the pressure on the gauge at the top of the filter. This is your starting or “clean” pressure. It is a good idea to take a permanent marker and mark this number. Now you will be able to determine when it is time to backwash. Remember, always backwash when the filter reaches 8 to 10 psi over this starting pressure.

Filter Facts

Pump: The pool pump pulls and pushes the water to the filter. In the front of the pump you have the pump basket which catches large debris before it enters your filter. After the water has made it through the pump basket, the impeller pushes the water up and out of the pump and into the pool filter

Pump Basket: Check the basket daily during the months the pool is in high use or when the leaves are falling and empty it whenever it is full. Not emptying the pump basket can result in water not making it through the pump and your equipment to run hot. If this happens the pump can seize up, stop working or melt from the extreme heat that is generated. Replace the pump basket immediately if it is cracked or broken. Failure to do so could result in damage to the pump or filter from large debris.

Pump Lid: A cover, normally clear, that threads or locks onto the top of the pump basket pot. It allows you to see debris in the pump pot and water flow. Under the top of the lid there is an O-ring. This should be checked and lubed with a silicone or Teflon based lube at least once a month. This will prevent cracking and create an airtight seal for the pump. Hand-tighten the lid; plus 1/8 of a turn; to completely seal the pump pot.

Filter: There are 3 main kinds of pool filters on the market today. They are sand, D.E. and cartridge. We will discuss how to clean these filters later in the school. For now, realize that the pool filter is where the “dirty” water from the pool flows in from the pump, the water is filtered through one of the three systems and then returns to the pool as cleaned, filtered water. When you open the filter there is a large O-ring or belly band seated between the top and bottom halves. This should be checked for cracks and lubed at least twice a year.

Chlorinator: Most pools using chlorine tabs will have an inline chlorinator where you add your chlorine tablets. There is an O-ring in the lid of the chlorinator that should be checked and lubed anytime the tablets are re-filled.

Multiport Valves: Sand and D.E. filters will have a multiport valve that will change the filtering options. This valve should only be moved when the pool is turned off and moved in one direction only. There is a “spider gasket” O-ring underneath the valve that should be checked a few times a year. This O-ring should be seated in place with silicone glue. Add a light layer of lube to the top of the spider gasket to allow the multiport valve to turn smoothly.

Automatic Pool Cleaners: Automatic Pool Cleaners: There are a multitude of automatic pool cleaners in use today. Let HERBS POOL SERVICE perform a free check up on yours. We recommend you bring it in to our shop once per year to have it checked for damage or wear and tear. Think of it like a car that needs yearly maintenance and upkeep. This will insure a long operating life for your cleaner.