Cleaning Cartridge Filters

Hosing-off a cartridge filter

Cartridge filters are somewhere between DE filters and Sand-filters in terms of efficiency and the size of particle that they can remove from your pool-water

Cartridge filters pack a huge filter-surface area into a very small space. Most cartridge filters have a filter area greater than 25 m2 (250 ft²) and need to be cleaned less frequently than sand-filters, reducing water-loss 

Some filter elements are inexpensive to replace but they don't tend to last as long. Other filter elements can be costly but will last for several years. Largely, you get what you pay for

In general terms, Cartridge Filters need to be cleaned only once or twice a season, simply by hosing them off with a garden hose. Do not use a power-washer as the force of the high-pressure jet can easily tear holes the cartridge elements, rendering them useless

However, sometimes a cartridge can become contaminated with sun-cream, etc., and in this case it should be soaked in a filter solvent, available from any pool-shop

Should you have a cloudy, green pool, however, the filter will clog more rapidly and need to be cleaned more frequently

Tip: - When replacing an old filter cartridge element with a new one, make a note of the pressure on the tank pressure gauge and mark the gauge with a PERMANENT marker pen

This reading is the lowest it is ever going to be as the cartridge has not yet collected any dirt and therefore the water passes through the filter membrane easily

Make a similar mark at approximately 0.5 Bar or 8 pounds per square inch (psi) higher than the first mark

These 2 marks represent the upper and lower limits of the normal operating pressure for your cartridge, in pounds per square inch (psi). Make a note of these 2 figures in your Pool Logbook

Clean the cartridge when the gauge reaches the higher pressure mark and, after re-fitting it, make a note of the new start-up pressure.  As the cartridge gets more use its efficiency will drop off and having the normal operating pressure data for your cartridge to hand will help you decide when the element needs cleaning again

Cleaning Instructions

Follow the manufacturer's instructions to remove the cartridge from the filter housing. If you don't have these instructions to hand you will almost find them online on the manufacturers' website.  Don't you just love the Internet?

  • Working from top to bottom, wash accumulated dirt from the element, paying particular attention to between the pleats, with a low-pressure garden hose
  • As stated above, do not use a power-washer or you risk destroying the membranes
  • Continue cleaning until all the dirt has been removed and the water runs clear
  • If the filter is clogged with oils, soak it overnight in filter-cleaning fluid or, alternatively make up a mixture of washing-up liquid and water
  • The home-made mix will not be as efficient as the proprietary products but will still do a pretty decent job
  • Rinse the cartridge thoroughly to remove cleaning solution residues and loosened dirt

Acid Washing of filter elements

Acid washing should only be carried out when it is calcified (perhaps from a too-high pH of the pool-water?) and the element should first be thoroughly cleaned, as above, with a hose and a cartridge degreaser first

You can easily discover if your cartridge would benefit from an acid wash by dripping one or two drops of 5% Hydrochloric (Muriatic) Acid/water onto the pleated element

If the acid produces bubbling your cartridge would probably benefit from acid-washing

If no bubbles form your cartridge would probably not benefit; rinse the cartridge again and re-install

Cartridge Acid Washing - Instructions

  • Make up a solution of 5% Hydrochloric Acid and water
  • Wear rubber gloves and eye-protection when handling acid or other pool chemicals
  • Note: add the acid to the water, not the other way round
  • Soak the cartridge in this mixture until all bubbling ceases
  • Rinse the cartridge again with fresh water from a garden hose
  • Wash your hand immediately after handling any pool chemical

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Ken Walker - MyPoolGuru©