Filter Maintenance

Cartridge Filter Maintenance

How to clean cartridge type filters

1. Rinse any debris from the filter with a garden hose and spray nozzle before the filter dries after you have removed it. Drying will allow the collected debris to set into the filter media, making it more difficult to remove later.

2. Allow the filters to dry thoroughly, preferably in bright sunshine, which helps kill algae.

3. Shake or use an air compressor to remove loose particles from the filter’s fabric. If using compressor, wear eye protection! This can also be done by tapping it on a surface, brushing with a stiff paint brush, or other means. Note that this step is in preparation for the actual cleaning, so getting it perfect is not necessary.

4. Save the filters you would normally throw in the trash until you have several to clean. Because cleaning involves using chlorinizer and takes time, cleaning individual filters is not efficient. five gallon/18.9 liter plastic paint bucket will hold about five type C filters.

5. Prepare a large bucket with a tight-fitting lid to soak your filters. Use a solution of 1 part pool chlorinator to 6 parts water. Submerge the filters in this solution, then place the lid on the bucket.

6. Allow the filters to soak to kill any microorganisms that are trapped in the filter media, and to break down any organic contaminants. One day is good, but 3 to 5 days will provide better results.

7. Remove the filters and rinse in a bucket of clean water. Agitate the filters by holding them at one end, and dunking them briskly in and out of the rinse water. You should see a cloud of rinsed contaminants coming from the filter.

8. Hang or place the filters in bright sunlight and allow them to dry thoroughly. Any more dirt that is trapped on the surface of the filter should be brushed off, using a stiff bristled paint or parts cleaning brush.

9. Seal the bucket you soak the filters in when not in use so you won’t have to add additional chlorinizer each time you clean filters. Some sediment will accumulate in the bottom of this bucket, but it doesn’t affect the cleaning properties of the solution.

10. Mix a solution of muriatic acid and water to dissolve minerals that accumulate in the filter media, reducing the rate water can pass through the filter. Use another clean bucket with a lid that seals tightly. Add about 2/3 of a bucket of clean water, then carefully pour in enough muriatic acid to give you a 1 part acid to 10 parts water solution. In a typical 5 gallon bucket, this means about 3 gallons of water to 1 1/2 quarts acid.

11. Soak the filters in the acid solution until it quits bubbling. The bubbles are an indication the acid is reacting with the mineral deposits, and when the bubbling has quit, the minerals should be dissolved.

12. Seal this container when you are finished with it. If you keep your containers sealed tightly, the chemicals (either the acid or chlorinizer) will not weaken and may be reused for several cleanings. Allowing the containers to remain open will allow the chlorine to evaporate out of your solution, rendering it useless in a short time.

13. Rinse the acid cleaned filters with plenty of fresh water, then allow them to dry, shake any remaining collected dirt from the pleats, and they are ready either to proceed to chlorine soaking, or if this step has followed the chlorine soaking, they are ready for reuse in your pool.

14. Reuse your cleaned filters.

Special Notes:

  • Pool filter cleaning chemicals are marketed specifically for cleaning cartridge type filters, but the cost is fairly high in consideration of their performance.
  • Make sure the filter/pump unit is working correctly before using shock or adding chlorine or other chemicals to the pool.
  • Store filters in a plastic bag or other container when they are cleaned to keep insects from making a home in them.
  • You may want to use a new filter instead of dealing with acids, having a sealed bucket of bleach around and using used filters.
  • Remove the collected dirt from the filter in stages, removing as much as possible in each stage. Simply tapping or brushing the filter after it has dried in the sun will reduce the amount of organic contaminants that need to be broken down in the cholrinator soak.
  • Filters may become clogged much more rapidly when using clarifier in the pool water, as this product will cause the particles that cloud the water to be trapped more easily in the filter media.
  • Discard any filters that become damaged or deteriorate to the point they no longer filter efficiently.
  • Using a 5% muriatic acid solution to remove calcium deposited in the filter media will increase the filter’s performance if high concentrations of minerals exist in your pool water.
  • For cleaning filters in pools where a large number of people swim, and suntan lotions or other materials may accumulate, using a dish washing liquid solution to presoak the filter may yield superior results.
  • Maintain your pool water chemistry to minimize the organic contaminants in the water, making the filter’s job much easier.
  • Remove and clean or replace the filter on a regular basis.

Sand Filter Maintenance

The logic behind never changing your filter sand is that dirty sand actually filters better than brand new sand.  The flip side to this is that after enough time the sand will no longer be able to filter the water well enough.  From a manufacturer standpoint it is recommended that you change the sand in your filter every 3-4 years.  This will maximize the effectiveness of the filter and help you to maintain clean and clear water.

1. Removing the sand with a shop vacuum will be much easier than scooping the sand out by hand or with a small shovel.  The sand in an old filter can actually be laden with bacteria so it would be better if you minimize your direct contact with the sand.

2. After removing the old sand you will want to add water to the tank before adding new filter sand.  This water helps to absorb any impact of the falling sand on the lateral assembly.  Many professional installers skip this step but that would not be recommended if this is your first filter sand change.

3. The type of sand that you add to the filter will be #20 silica sand which is specifically produced for filter media.  This sand is between 40-50mm in diameter and is available from most swimming pool supply stores.  Do not substitute other types of sand or you will almost certainly have problems with your filter and potentially damage the pool also.

4. The amount of sand that you add to the filter will depend on the size of filter that you have.  You must be certain to find accurate information about how much sand to use in your filter.  Over filling or underselling the filter will at least cause the filter to not function properly, and at worst cause damage to the filter.  Filter sand sizes range typically from 100 or 150 lbs all the way up to 600lbs or more for large pools.

5. Be sure not to get any sand into the sandpipe which will be wide open.  It is difficult to get the sand actually into the filter without getting it in the sandpipe so you may like to tape up the standpipe opening to prevent this spilled sand from making it back to the pool through the return lines.  It is also very important that the sandpipe is directly in the center of the filter as once you have filled with sand you will not be able to adjust the position of the sandpipe.  If not centered you will not be able to get the valve head back on the filter and will need to start all over again.

6. Once full you can put the filter head back on being absolutely certain that it is tight enough.  This is where a skilled hand is helpful as if you overtighten the filter head then you may actually  crack the filter body which would require replacement of the entire filter tank – something you definitely want to avoid.  

7. Once back together the first thing you need to do is give the filter a thorough backwash.  You should start this process by over filling the pool and then backwashing for as much as 3 to 5 minutes, followed by a 60 second rinse cycle before setting to “filter”.

NOTE: It is normal to have some sand back into the pool or out through the waste line when you change your filter sand as some of the sand that you received will be smaller than #20 and this smaller sand will eventually work its way out of the filter.  The long initial backwash that you do when you change the sand will help to minimize this.

Diatomaceous Earth Filter Maintenance

Run filter system 1 hour for every 10 degrees of outside temperature:
Summer 8 to 10 hours per day, winter 4 to 8 hours per day

(If pool looks cloudy, run filter until pool clears- then go back to your regular schedule)

 How to Backwash a Diatomaceous Earth Filter (If your filter requires it, some like Hayward don’t)
Most filter manufacturers recommend backwashing after a clean filter has built up 5-10 PSI of pressure as indicated on the pressure gauge. D.E. filters typically build up these pressure levels in approximately 1 to 3 months. Over backwashing can lead to algae problems in the heat of the summer due to the loss of important chemicals. Avoid backwashing within 12 hours after your pool has been chemically serviced.

**Never move the backwash valve when the pump is running (this will break the parts inside the filter)**

1. Shut off the pump
2. Turn the multi port or valve handle to the backwash position
3. If necessary, roll out your backwash hose or open valve on backwash line
4. Turn on the pump and run system for 1-3 minutes or until water in the sight glass or discharge hose turns clear
5. Turn off the pump
6. Place the valve handle in the filter position.
7. Redo the first steps, two to three times, this will loosen up debris and remove more dirt at each backwash cycle
8. Place the multi port valve handle back in the filter position
9. Turn on the pump
10.Wear a dust mask when working with D.E. powder! Coat the filter grids with D.E. powder by adding the recommended amount through the skimmer.


Diatomaceous Earth (D.E.) filters use a powder called diatomaceous earth to strain out the small tiny particles that pass through the system. This product is very inexpensive and readily available at home and garden centers. Each time you backwash a D.E. filter, you will flush out both accumulated dirt and debris and spent D.E. from the filter canister. Failure to replace the canister with fresh D.E. can cause severe damage to the internal elements of the filter and will leave the filter virtually non-effective, since the earth is the primary filtering agent.

There is a simple formula to figure out how much D.E. should be added to your filter. First, determine the size of your filter. The square feet of filtration area inside the filter canister determine filter size. This number is found on a specifications plate on the front of the canister. (Most filters carry a filtration area of 36, 48, 60, or 72 square feet.) Using a one-pound coffee can, add one can of D.E. for every 5 square feet of filtration area. It’s OK to round off to the nearest multiple of 5; the filter won’t mind a little extra D.E. A 48 square foot filter requires 10 cans of D.E. A 36 square foot filter will function effectively on 7 cans of D.E.


Maintenance for a D.E. Filter
Even with regular backwashing, D.E. filters accumulate debris and it is a good idea to have your filter dismantled and cleaned at least once a year. This affords an opportunity to check internal elements for wear and tear, and to ensure that the filter is working at peak efficiency.