Swimming Pool Blog

Pool Filter Repairs and Maintenance

Pool Filter repair and maintenance

by Sean Griffin, January 5, 2012

Pool Filter Repairs and Maintenance

pentair filtersWithout proper filtration even the most chemically balanced pool water will eventually become cloudy and un-swimmable. Your pool pump is the heart of the swimming pool equipment and your pool filter is the kidney (you only need one). Both are vital to properly maintain clarity in any body of water. Every filter on the market, regardless of the media being used,  will require maintenance and from time to time may call for a repair. For most homeowners the difficulties in ensuring your pool filtration stays optimal lies in diagnosing a water filtration issue when it occurs. Knowing what to look for and timelines on certain filtration components that need to be serviced or replaced will help save you some time and money and instill the confidence you need to make the repair yourself.

Every pool owner should be proactive instead of reactive when it comes to ensuring pool water quality. Preventing problematic water will prevent excessive and costly chemicals that may be needed to restore pool water that has become unbalanced and unfiltered. Knowing the limitations of your pool filter and the ability of the filtering media within will be key in keeping things crystal clear.


Filtration of water using sand dates back to 2000 B.C. Sanskrit writing outlined water purifying methods before bacteria and micro organisms were known to man. These same principals associated with water filtration have been incorporated across the world throughout time.

Modern sand filters for commercial and residential pools commonly use #20 Silica sand or Zeobest. Zeobest is an alternative to sand with a higher surface area which allows you to use less within the filter and also achieves a higher microscopic filtration rating.

Routine maintenance will include backwashing the filter once the sand bed has captured particles and the pressure within the filter tank has climbed 5-10 psi. How often you will need to backwash your pool filter will depend on what is introduced into the pool water. Backwashing is performed by reversing the flow of water to force out the unwanted filtered particles.

The most obvious sign of a problematic sand pool filter is sand entering the pool. You may notice a massive amount enter the water after backwashing your filter or it may be less significant and may take time to build up to even be noticed. The sand within your filter tank is not intended to enter the pool water. Sand entering the pool can mean a couple different things. Laterals that lay beneath the sand bed may have become brittle and cracked allowing the sand to flow through the filter. Sand itself over time can erode under pressure and create smaller particles of sand which the filter is not capable of retaining. Every pool is slightly different but the media inside a sand filter will need to be changed every 5 or so years.

Another sign the filter may be having an issue is water clarity. Sand filters are subject to mud balling and channeling. An even or flat sand bed means ideal filtration. Things that are introduced into the filter like lotions and oils can cause coagulation of the sand particles which will allow water to flow more freely, bypassing some of the filter sand. To diagnose you may have to open up the filter and inspect the sand bed.

Early indications of sand filter issues can be cloudy, unclear and unfiltered water. The tank pressure will not rise properly as contaminants are not being removed. Before you look into your sand filter you will want to rule out a pump or valving issue. Make sure the pump flow rate is correct and the multiport or push-pull valve is not allowing water to bypass the filter.

Replacing the filter sand, cracked laterals, or a damaged stand pipe can easily be achieved by a DIY pool owner. If you have a top mount sand filter it is recommended to have unions on all connecting lines so you may access the interior workings. If you have to cut any plumbing make sure to add some unions so you don’t have to deal with it again in the future.


A cartridge pool filter will utilize a paper element filter that will capture the particles that are forced through the filter. Although similar in design to a sand filter the maintenance and repair issues differ from that of a sand filter. A cartridge filter will build up pressure internally just like every pool filter. A cartridge filter does not utilize backwashing and reversing the water flow through valving is obsolete. Instead manually cleaning a cartridge filter is necessary once the filter build up pressure due to capturing those pesky particles. The lifespan of a filter cartridge will depend on routine maintenance as well the demand that is put on the filter.

Cleaning your cartridge filter can be achieved several different ways. For light debris and sediment that falls off the element fairly easy a high pressure hose nozzle or water blaster can quickly get your filter cartridge back to looking white and clean. Cartridges are often subject to organic staining which will require a filter cleaning chemical or a muriatic acid to water mixture to burn off the brown staining.

The most common of cartridge issues is the deterioration of the paper element filter within. Over time, under constant pressure and exposed to the affects of pool water chemistry a cartridge can collapse and water passing through the filter will not run evenly between the individual pleats. Signs of a problematic filter cartridge are usually visible on the cartridge itself. A consistent high pressure even after a cleaning is a good indication the filter cartridge needs to be replaced. If a cartridge has collapsed or has been stained to the point of clogging, you can actually do more damage than good by using the filter cartridge.

Diatomaceous Earth 

Arguable the best filtration method, D.E. filters have the capability of filtering down to the smallest micron. An internal grid assembly that consists of several filter elements is coated with diatomaceous earth. This media, which is similar to crushed up sea shells, filters out all unwanted particles. When the pressure rises within the filter the media has been exhausted and will need to be flushed out and replaced. From time to time it may be necessary to manually remove the grid assembly and clean with a high pressure water nozzle. Signs of damage to the filter grids can be staining of the material, a collapsed skeleton (the lattice of the grid), and frayed or torn material.

Most home owners will notice diatomaceous earth return to the pool when the filter is in need of a repair. If the multi-port or slide valve is functioning properly this means the media is bypassing the filter. Common places to inspect should be the grids themselves, the grid manifold, and where the manifold rest on the standpipe. I have seen pool filters that have run for an extended period of time at a high pressure that can cause the manifold to implode inward, cracking, and allowing DE to bypass the filter. Another common route for the DE to make its way back to the pool is an internal air bleeder that assists trapped air to make it to the top of the pool filter and escape. Make sure any air bleeder tube or assembly has not become dislodged or damaged.