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How Does A Pool Sand Filter Work?

April 6, 2021

Pool sand filters are one of the most convenient and efficient ways to keep your pools clean. This type of filter utilizes sand as a filtering agent; because of this, sand filters are known to run for a long time with little maintenance required to be in top-notch condition. With all of the benefits mentioned, we recommend getting a pool sand filter for your home. 

But how does this pool sand filter work? In this article, we will guide you through how this filtration system works and how to maintain one.

Pool sand filters, as mentioned earlier, use sand as their filtration agent. It works by allowing your pool water to flow through the sand filter canister that contains the sand. Typically, water will pass through the sand filter, but larger particles will be filtered, trapping them inside the canister. Once this process is complete, a pump will return the clean water to your pool. One of the good things about pool sand filters is that as it builds up debris inside the canister, the filtration's efficiency also increases since the debris will help filter smaller particles from the water. 

Keep in mind that you can’t just use any sand in your pool sand filter system. You must use a specific type of sand to have maximum filtration efficiency. Commonly, pool sand filters use #20 silica sand with grains with the size of 45 to 55 millimeters, and the good news is most of the pool sands and filter sands fit these criteria since those sands are specifically made for pool sand filters.

What Materials are Filtered By the Pool Sand Filter?

A wide variety of materials can be filtered through your pool sand filter. It would range from larger materials such as leaves to even smaller particles that range from 20 to 100 microns in size and won't pass through the sand filter at all. And as the debris in the filter builds up, smaller particles than 20 microns can also be filtered as your pool sand filter runs.

Maintaining Your Pool Sand Filter


Even though your pool sand filter gets more efficient as it filters your pool water, there are limits to how much it can filter, and it needs to be cleaned as well. As your pool sand filter collects debris, the pressure inside the canister will begin to rise as well. You will need to monitor the initial reading of the pressure gauge on your pool sand filter, then check it once or twice a week to see the increase in pressure. If the pressure reading has increased by 8 to 10 pounds, you will need to “backwash” your pool sand filter to clean and remove the excess built-up debris. To perform a backwash, you need to shut down the pump that cycles water throughout your filter. Then unroll (if it is already attached) or attach the backwash hose into your pool sand filter and turn on the backwash valve. Turn the pump back on and let it run. Do not worry if it suddenly became darker after the initial clean water, it's just the excess debris being cleared out from your pool sand filter. Shut the pump off when the water becomes clear, then turn on the “rinse” setting on the valve and allow the cycle for 40 seconds. After you have done all of this, roll the backwash hose again, reset the pump to its normal setting, and restart the pump.

Changing Your Pool Sand Filter's Sand

Backwashing sometimes won’t be enough to maintain your pool sand filter’s efficiency forever, especially if your pool sand filter is already running for years. When this happens, you should consider changing your sand inside the sand filter. This procedure is easy to do depending on your canister's size and will only have to be done every 5 or 7 years. To start things off, perform a regular backwash but turn off the pump once it is finished. Then open the pressure valve, which is located at the top of the filter, releasing pressure from the sand filter. After that, open the drain valve at the canister's bottom to remove the water inside the canister. While holding the canister, loosen the bolts holding the canister in an alternating manner to prevent damage to the canister by avoiding too much stress on one side. Then after removing the top of the canister, scoop out the sand inside the canister. When all of the sand was removed from the filter, check the filter's inside for broken or loose components. Replace or fix if any parts are broken or loose to prevent further damage to the filter. To put clean sand inside the canister, make sure that the canister is half full with water. This prevents damage as you start to add sand into the canister. After that, pour or scoop new sand into the canister within two inches of the top. If unsure how much sand you will add, consult the pool filter’s manual to ensure you add the right amount of sand. Once the canister is filled with sand, reattach the canister's top and then perform another backwash before using the sand filter again.

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