A Guide to Selecting the Best Pool Filter

Filters help remove and keep contaminants out. Cars have filters for air, oil, and transmission fluid. Filters in clothes dryers catch lint. Vacuum cleaners capture dust in their filters. Coffee machines use filters to keep the grounds out of coffee. The same is true for swimming pool filters. While sanitizers like chlorine kill bacteria and help break down contaminants in a swimming pool, filters are what actually remove these impurities. Without a filter, pool water will get cloudy and the pool will soon fill with debris. The best pool filters depend on several different factors, including the size of the pump and the swimming pool.

Choosing the Best Pool Filter

There are three basic swimming pool filters, each with advantages and disadvantages. These include cartridges, DE (diatomaceous earth), or sand pool filters. These vary considerably from each other, and choosing the best pool filter involves considering a variety of factors.

These include:

  • Cost of maintenance and pool filter parts
  • Ease of use
  • Filtration rates needed
  • Initial cost
  • Pool type
  • Replacement frequency
  • Size

The best pool filter depends on which factors are most important to the pool owner or operator.

Best Pool Filter for Pump and Pool Size

Two other factors pool operators need to consider when choosing swimming pool filters are the size of the pump and the pool it will filter. The filter will not function correctly unless sized for the pump. Swimming pool filters should also be able to handle the rate at which the pump runs, which is why filters are rated on the gallons per minute (GPM) they can handle. These rates must match the GPM of the pump, though erring on the larger side is recommended. A filter size should be at least one square foot per ten thousand gallons of water. However, it’s a good idea to seek advice from a reputable pool supply company if uncertain about the size.

Cartridge Swimming Pool Filters

The ideal pool filters when it comes to convenience are cartridge filters. Slightly more expensive than other swimming pool filters, cartridge filters tend to be more effective and energy-efficient than less expensive ones. They are also relatively easy to maintain, with pleated elements that are easily removed and rinsed. Cartridge swimming pool filters need to be replaced regularly, though how often depends on the pool’s location and what other cleaning methods are used for the pool.

Advantages of cartridge swimming pool filters include:

  • Filters contaminants 10 microns and larger. ‘
  • Recommended for pumps that operate at variable speeds.
  • Requires no backwashing, so wastes less water.
  • Works well at low speeds.

Disadvantages of cartridge swimming pool filters include:

  • Requires more work than other filters.
  • Needs to be deep-cleaned once or twice yearly.
  • Lasts on average from 2-3 years.

These are the best pool filters for highly trafficked pools, such as public pools or those found in hotels and apartment complexes

Maintaining Cartridge Filters

Rather than backwashing, which uses a lot of water, cartridge swimming pool filters should be removed from the tank and cleaned regularly. Generally, this just involves hosing it down to remove dirt and other debris. Occasional spraying with filter cleaner is also recommended, as is soaking the cartridge in diluted muriatic acid or a chemical cleaning solution for filters.

Diatomaceous Earth Swimming Pool Filters

The grids of DE swimming pool filters are coated with diatomaceous earth, a fine powder made from crushing the fossils of tiny aquatic organisms called diatoms. Diatomaceous earth is essentially silica, a substance commonly found in sand. These filters pick up dirt and sediment invisible to the naked eye, allowing it to filter finer materials than other options. However, as DE pool filters run at high pressures, they tend to be less efficient and can cause flow loss. They are also the most expensive option.

Advantages of DE swimming pool filters include:

  • DE powder can be added via the pool skimmer.
  • Filters contaminants 5 microns or larger.
  • Requires no caustic chemicals when cleaning.

Disadvantages of DE swimming pool filters include:

  • Difficult to find the right DE filters for above-ground pools.
  • The grid needs replacing every 2-3 years.
  • High cost.
  • Inhalation of DE powder can cause harm.
  • Requires intensive cleaning on annual basis.
  • Some localities restrict backwashing.

Maintaining DE Filters

A pressure gauge on the tank indicates when it’s time to clean the filter. This requires backwashing, though some types of DE filters have a bump handle that makes it easier to shake off the used DE powder from the filter’s grids or fingers. After cleaning, more DE powder needs to be added. Disassembling and cleaning the filter by hand at least once annually will make sure there’s sufficient DE powder for filtering purposes.

When adding additional DE powder, it’s best to use a pool skimmer. This involves mixing enough DE powder into the water until it becomes a thin and creamy solution. Pour this mixture directly into the skimmer while the pump is running. This ensures it distributes evenly over the grids. The best time to do this is in the evening, as the solution needs to properly attach to the filter before swimming.

Sand Swimming Pool Filters

Swimming pool filters often use sand as a medium for filtering pools. With sand filters, water flows through a bed of sand, trapping dirt and other debris within the grains before returning the water to the pool. Each grain of sand is jagged, and these jagged grains are what captures contaminants. As contaminants build up within the filter, this helps it capture even smaller particles.

Advantages of sand swimming pool filters include:

  • Do not clog as easily.
  • Easy to maintain.
  • Low cost.
  • Sand media lasts between 5-7 years before it requires changing.
  • Using different media or additives can boost efficiency.

Disadvantages of sand swimming pool filters include:

  • Greater pressures decrease the efficiency of the filter.
  • Involves more water to backwash and rinse.
  • Only filters debris of 20 microns or more.
  • Requires more attention paid to pool chemistry.

Because they do not clog easily, these are a great option for larger pools.

Alternatives to Sand

The standard media for sand filters is #20 silica. Adding DE powder or replacing the sand will increase efficiency somewhat. However, it’s possible to replace this with either zeolite or filter glass. Zeolite – also known as ZeoSand – requires only half as much as standard sand for filters; it traps smaller particles, while its lifespan is similar to regular sand. Filter glass comes from recycled glass that is crushed finely. It lasts three times longer, while also filtering debris a quarter of the size of regular sand and requires about a fifth less.

Maintaining Sand Filters

Sand swimming pool filters require little maintenance. Unlike DE powder, sand only needs replacing every several years. They are the least expensive and easiest swimming pool filters to maintain. Pressure gauges on the filter’s side alert when internal pressure increases, indicating it’s time to backwash. Over time, however, the surfaces of sand grains erode, becoming smooth. When they do, the sand requires changing.

Maintaining a Swimming Pool Filter

Due to the important role swimming pool filters play, it’s important to keep them well-maintained. There are a few common problems even with some of the best pool filters. Dealing with these issues involves a bit of troubleshooting and, in some cases, may require pool filter parts.

Leaking Filters

Dripping water around the swimming pool filter or small puddles forming below may indicate the filter’s got a leak. Though it won’t cause water levels to drop, it should be dealt with swiftly. First, check for any holes in the filter tank and patch them. Likely these won’t hold, but it will keep the tank from leaking until it can be replaced.

For split tank filters, check the belly for any leaks. By removing the band, the O-ring can be inspected for wear or debris that may have dislodged it. If it’s worn, it needs replacing. When doing so, add lubricant designed for pool gaskets to help seal it, keeping the ring hydrated to make it last longer.

Cycling Issues

When a swimming pool filter runs on shorter cycles, even when the pool isn’t being used, it indicates a possible problem with flow rate. This often occurs when the pool pump’s too strong for the filter, or if the filter is too small for the pool. For correctly sized pool filters, this may just indicate the need to backwash for a longer period. Another factor may involve algae or other debris clogging it, which requires thorough cleaning to resolve.

Filter Material Infiltrating Water

After backwashing, seeing filter material in the pool water isn’t uncommon. When such material appears when the pool hasn’t been backwashed, it may indicate a problem. First, check the bolts holding the filter in place. If loose, this may be the culprit. For sand swimming pool filters, it may indicate that the filter lateral or standpipe has broken, For DE filters, the grid’s fabric may have torn, a crack may have developed in the manifold. If something’s broken, it means replacing these pool filter parts.

Problems with Water Pressure

Part of regular swimming pool maintenance involves checking the pressure gauge. This can affect a pool filter’s performance. If pressure is too low, it may indicate a blockage before the filter, while if pressure is too high, it could indicate a blockage after the filter. If the filter’s clogged, it must be cleaned. If no clogs are found and the filter’s cleaned, check that the return valve is open then double-check the lines for clogs.

Contact Halogen Supply

Since 1939, Halogen Supply Company has been a “one-stop-shop” for all your pool filter needs. For questions or to inquire about our products, please contact our expert team today!