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Pool Filters: How to Choose


Pools have several moving parts, and today most of those features can be controlled with a phone app. Yet another wonderful luxury, courtesy of technology!

In your backyard paradise, your pool’s filter and pump are at the heart of it all. If the proper one isn’t installed or appropriately maintained, you’ll be swimming essentially in gunk. While the carefully metered chemicals make their contribution, it’s the filter that does the heavy lifting by removing contaminants from your pool’s water.

Amongst the assortment of filtration alternatives, your objectives are crystal clear. You want your pool’s filter to:

  • Be easy to maintain
  • Be the most cost-effective for your budget (without skimping!)
  • Effectively trap impurities
  • Have enough staying power to last more than three seasons

Before we take a look at some filter types which will help narrow the options between cartridge, sand, or DE (diatomaceous earth) filters, note that this equipment is sort of “micron-rated” denoting the unit’s capability to remove contaminants.

Bacteria comes in all sizes, so you’ll want to know how efficient your chosen filter is based on the smallest micron it can trap for the cleanest possible pool.

Cartridge Filters

Relatively easy to maintain but a little more expensive than their sand filter counterparts, these cartridge filters are typically recommended for a small to medium size pool.

As the name implies, a plastic cylinder is surrounded by a pleated, polyester cartridge to increase the surface area. Water flows into the tank and courses through those pleats. After a simple capture, typically at 10 or so microns, and then your cartridge filter will route that clean water back in to your oasis.

Regarding price, these cartridges are pretty inexpensive, while the maintenance couldn’t be easier. Just release the cartridge from its tank, spray down with your garden hose, and replace. (With no backwashing required to get it clean, you’ll save on water.)

We recommend you rely on your pool store resource or the manufacturer’s maintenance tips to advise how often you’ll need to use a filter cleaner and/or to give it a soak based on the filter brand and your pool type. You’re probably just looking at every six months for this step.

Sand Filters

For an inexpensive solution to pool filtration, tipping the scales toward the most minimal maintenance is the sand filter. Unlike the cartridge filters that should be restricted to small and medium sized pools, sand filters are ideal for large pools. One of the reasons being, they won’t clog as easily, managing all that extra water.

The way this solution works is your pump pulls the water, guided by the skimmers, and routes it to a tank that is filled with sand instead of a pleated polyester filter. The particle capture size here is roughly 20+ microns.

What’s unique about the sand is that the outer coating of the grains is not smooth, but rough. Those little “imperfections” are what catch those unwanted pollutants to pass them along to the filter.

However, like the effect of erosion by water, those rough edges will eventually wear down, rendering the grains inadequate for your pool’s filtration needs. Additionally, the accumulation of trapped particles will also ultimately inhibit the flow through the filter thereby degrading its effectiveness.

Unlike the cartridge filter, in this scenario you’ll have a gauge that will monitor the pressure build alerting you to backwash the filter. The sand itself (there are multiple types from which to choose) should remain useful for five to seven years before it needs to be replaced.

Note also that because the particle capture size is 20 microns and greater, you will need to compensate with chemicals to rout out those smaller particles that will escape the sand.

DE Filters

At the other end of the expense and maintenance spectrum you’ll find diatomaceous earth filters. While these are pricey and require more than the typical filter upkeep, these filters also yield the best trap rate on particles at five microns.

They do it via tank-encased grids dusted in a powder. According to The Spruce, this powder is actually “a soft, crumbly sedimentary rock composed of chemically inert, fossilized (or skeletal) remains of billions of microscopic algae-like organisms, called diatoms.”

So, the DE filters pump the water through a filter canister filled with DE which “has particles considerably finer than sand and with a structure better suited to capturing contaminants. Many pool owners and pool maintenance workers, therefore, consider DE filters to be the best type for residential swimming pools.”

Similar to sand filters, you’ll benefit from the existence of a pressure gauge on the tank alerting you when the filter needs to be cleaned. You do have some options here as these filters can be backwashed, or you can use what’s called a bump handle (if your filter is so equipped). “Bumping will regenerate the DE currently in the tank and can extend time between backwashing cycles, saving you money by reducing the amount of Diatomaceous Earth used throughout the season.”

Every time you do clean, (backwash or bump) you will need to supplement the DE powder. As this is not an exact science, it does inspire you to take the filter apart and hand clean it at least yearly. When replenishing, follow the manufacturer’s instructions to the letter so you get the right ratio of water to DE and also to get the best possible coverage on the grids when the mixture is added to the skimmer.

It’s recommended that the DE be added in the evening when you’re done with the pool for the day. By running the pump overnight, you have the best chance of an even distribution of the blend.

Make certain to find out about any local ordinances (that bear fines!) governing the disposal of DE. Backwashing can cause the powder to build up, leaving concrete-like deposits that can clog storm drains and affect aquatic life. There are safe, acceptable ways to easily dispose of DE in separate containers for deposit in the regular, non-recycle, trash.

Regarding the replacement, you’re looking at every two to three years. A very important caveat is that DE powder can be harmful if inhaled, so it is recommended that the proper mask be worn when working with this substance. Give DE the same reverence you give any pool chemicals by handling them properly and stowing them safely.

Just like a fine automobile with high repair costs, you’ll want to care for this filtration system well, so it takes care of you and also so it doesn’t need an emergency service call on a Saturday when you’re revving up for a pool party!

Bottom line… listen to the experts to guide you on the best filtration and pump solutions for you and your pool.

Providing pool and home improvement loan solutions since 1979, Lyon Financial loves backyard pools. We also love the difference we can make for your family by providing something that puts years of memories within reach. Call 877-754-5966 for more information about creating your ideal backyard oasis.