How to Clean Your Pool Filter

When people imagine a swimming pool, they imagine crystal clear water with a faint smell of chlorine, and shadows gently dancing on the concrete bottom. But that water quality does not come automatically. The pool filter plays a huge role in providing a safe, enjoyable experience for swimmers.

While many of the ins-and-outs of pool maintenance seem complicated, filter maintenance is not only straightforward but critical. Proper care can keep your filter running smoothly for years with relatively minimal work. Neglecting filter maintenance, on the other hand, can give you an unexpected headache or two.

What Does the Filter Do?

Summed up simply, the filter keeps your pool healthy. While the most apparent functions might include filtering out large debris like leaves and bugs (which it certainly does), it also filters out much finer things like dirt and dust, which can invite bigger problems when left unchecked. A few different filter types exist, but the basic mechanics remain the same.

Pool filtration systems essentially force water through some type of material porous enough to allow water molecules through, but condensed enough to trap larger objects trying to pass through with the water. By doing so, they reduce the amount of “junk” floating around in your pool.

Filters that fail to trap all of the particles end up placing a heavier load on the pool sanitizer since the chemicals go to work trying to dissolve all of the unwelcome things like bits of leaves, dust, or dirt. This creates issues wherein more chemicals may need to be applied, and the pool maintenance costs – both time and money – can arise.

Kinds of Filters

Filters come in a few different styles: sand, cartridge, and diatomaceous earth (D.E.) filters. There are pros and cons to each, but each of them provides essential protection to your pool water. You should consider what type of debris your filter will be handling, and how much you’re willing to spend.

Sand Filter

Sand filters come with the lowest price tag, but with the proper maintenance, they can still do an excellent job keeping your pool clean and last for years. They do have one drawback: the large pore space between sand grains means they function a little less effectively than other filter styles – at least initially.

However, that same drawback also means that sand filters become more effective over their first few years. Trapped debris decreases the pore space, but the effect does start to reverse as the grains wear down and lose their jagged edges. Sand needs to be replaced every five to seven years.

Cartridge Filter

Cartridge filters offer an even simpler filter to clean and filters out smaller particles than sand right off the bat. Cartridge filters generally filter out much smaller particles than sand filters. Unlike both sand and D.E. filters, which need to be backwashed (which uses lots of water – more on that later), cartridge filters can simply be removed and rinsed off.

While this cleaning process is simpler, these filters need maintenance a few times a year. Users pay for this simplicity with a higher upfront cost, and unlike inexpensive sand, the whole cartridge needs to be replaced every 3-5 years. Still, better filtering and decreased water demand for cleaning make it an excellent choice in many cases.

Diatomaceous Earth (D.E.) Filter

D.E. filters use the fossilized, microscopic shells of diatoms to filter pool water. The tiny, hollow shells trap the smallest particle sizes, making D.E. filters the most effective at trapping debris. D.E. filters are also the most expensive, and like sand filters require backwashing to clean. Additionally, some restrictions exist on the disposal of spent D.E.

D.E. filters work by having the actual powdery earth sit on a grid or finger assembly. The D.E. itself is sold separately and needs backwashing every 4-6 weeks. The grid assembly needs to be cleaned annually, making D.E. filters a little more time consuming to maintain. But they do create the cleanest pool water, so some users find the extra time and cost well worth it.

Cleaning Sand Filters

First and foremost, cleaning a sand filter requires knowing when the filter should get cleaned. Your pool gives two main indicators: a reading on the pressure gauge 8-10 PSI above the normal operating level (which varies depending on the filter), or cloudy pool water. When either of these conditions develops, it’s time to follow the steps below.

Gather the Equipment

  • Backwash hose
  • Sand filter cleaner
  • Filter owner’s manual

Cleaning a sand filter does not require much equipment, but the owner’s manual may come in handy if something goes wrong during the process.

Start Cleaning

  • Turn off the pool pump. This step is crucial, as turning the valves on the filter with the pump still running can damage the internal components.
  • Attach backwash hose, or unroll if already attached to the waste line and open the waste line valve.
  • Turn the valve on the filter to the “backwash” setting.
  • Turn on the pump to get the water moving backward through the filter.
  • Run the pump on the backwash setting until the water flowing from the waste line runs clear – usually just a few minutes.
  • Turn off the pump.
  • Turn the valve on the filter to the “rinse” setting to resettle the sand.
  • Turn the pump back on and rinse for 30-45 seconds.
  • Turn the pump back off.
  • Turn the valve on the filter to the “filter” setting.
    • Once a year, remove the filter basket during this step and pour in the sand filter cleaner.
    • Turn on the pump just long enough to move the cleaner into the sand.
    • Turn off the pump and let the sand soak in the cleaner for 8 hours or more.
    • Repeat the backwash process to remove any material dislodged by the sand filter cleaner.
  • Turn the pump back on.

Cleaning Cartridge Filters

Like sand filters, cartridge filters need to be cleaned whenever the pressure gauge rises 8-10 PSI above its normal operating levels. Even if the pressure stays at a reasonable level, cartridge filters should be cleaned at least every six months.

Gather the Equipment

  • Garden hose
  • Spray nozzle
  • 5-gallon bucket
  • Filter cleaner
  • Silicone-based lubricant
  • Owner’s manual

Start Cleaning

  • Turn off the pump to avoid damaging equipment.
  • Open up the air relief valve on the filter.
  • Remove the housing containing the cartridge.
  • Carefully remove the cartridge.
  • Inspect for any signs of damage – tears or very soft pleats indicate it’s time to replace the cartridge.
  • Use the garden hose and spray nozzle to rinse off the cartridge, making sure to get into all the small spaces between the pleats.
  • If necessary, apply cartridge filter cleaner directly or soak the cartridge in the cleaner overnight in the 5-gallon bucket, depending on the type of cleaner used.
  • Inspect the O-ring on the filter tank; if dry-rotted or damaged, replace it. If not, apply a thin layer of the lubricant.
  • Return the cartridge to the housing and reassemble the filter.

Cleaning D.E. Filters

D.E. filter cleaning has a little more involvement. D.E. filters are cleaned both chemically and with a backwash like a sand filter. Check your local municipal guidelines for information on the disposal of spent D.E. These filters need to be backwashed once a month or whenever the pressure gauge rises to 8-10 PSI above the normal operating level.

At least twice a year, you’ll want to do a thorough cleaning of D.E. filters following the steps below.

Gather the Equipment

  • Backwash hose
  • Garden hose
  • E. filter cleaner
  • Silicone-Based Lubricant
  • Replacement D.E.
  • 5-gallon bucket

Start Cleaning

  • Backwash the filter, using the same instructions outlined for sand filters above.
  • After backwashing, turn the pump off again.
  • Open the air relief valve.
  • Drain the water from the filter tank by removing the drain plug.
  • Open the filter tank and remove the grids and manifold.
  • Inspect the grids and manifold for signs of damage; replace if anything looks wrong.
  • Rinse out the filter tank with the garden hose.
  • Rinse off the grids and manifold thoroughly, using a D.E. filter cleaner if necessary.
  • Place the clean grids and manifold back in the tank.
  • Inspect the O-Ring on the filter tank and replace it if damaged.
  • If the O-Ring is in good repair, apply a layer of lubricant to keep it that way.
  • Reassemble the filter.
  • Add new D.E.
    • Follow the manufacturer’s instructions to mix the D.E. into a slurry.
    • Remove the strainer housing lid and fill strainer housing with water.
    • Put the strainer housing lid back on.
    • Open filter air-relief valve to remove air from the tank.
    • Turn on the pump.
    • Close the air-relief valve once the water starts flowing.
    • Slowly add the slurry directly to the skimmer with the pump running.

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Final Thoughts

Clean filters are a crucial part of pool maintenance. Thankfully, most filter designs make it easy for homeowners to take care of it themselves with a little know-how. Follow the steps outlined in this article, and you’ll be back to sparkling water in no time.

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