How does the Swimming Pool Sand Filter Works?

Sand filters are a popular choice for keeping swimming pools clean. These filters use natural sand as a filter, trapping debris as it passes through, so only clean water is pumped into your pool.

Because sand filters have no paper or fibrous parts to clog or tear, they typically last for years and require very little maintenance to stay in good operating condition. If you're looking for a pool filtration solution, take the time to consider the benefits of a sand filter to see if it's right for you and your pool.

Sand filters work by circulating water through a tank containing sand. Water can easily flow through the sand, but larger particles cannot. Once the debris and other particles are filtered out by the sand, the pump moves the clean water back into the pool. The filter's efficiency will also begin to increase as more debris is collected by the filter; the debris actually helps keep smaller particles from passing through the sand.

To ensure consistency and to ensure that most, if not all, debris that may be present in the pool water are filtered out, sand of a specific composition and particle size is used. Sand filters use #20 silica sand in the 45 to 55mm range. Any sand you purchase as "pool sand" or "filter sand" will meet this standard.

Your sand filter will capture a range of materials. Larger materials such as leaves, gravel, and insects simply cannot pass through the sand, and even smaller materials are blocked when the water in the pool flows through the canister.

Even small particles between 20 and 100 microns in size are captured by the sand inside the sand filter, and when the filter collects debris, it may contain particles smaller than that size. Particles that pass through the filter initially may be filtered out later as the water in the pool circulates back to the filter.

Because sand filters trap material, they require occasional cleaning and maintenance. The more dirt and debris there is in the filter, the more pressure starts to build up in the canister. Take the initial reading of the pressure gauge on the pool sand filter, then check it every two weeks to see if the pressure has increased.

Once the pressure has increased by 8 to 10 pounds, you will need to clean the filter by performing what is called a "backwash cleaning" to remove excess dirt and other debris from the sand. Backwashing the sand filter is easy. Turn off the pump to circulate water through the filter and let it stop completely. After the pump has stopped, unfold or connect the backflush hose and turn the pump's setting valve to "backflush".

Turn on the pump and let it run, and the water will start to clear, then it will start to darken as more dirt and debris come out. Let the water continue to flow until it becomes clear again, then turn off the pump. Turn the setting valve to the "flush" position and let the pump run in the flush cycle for 30 to 45 seconds. After flushing the filter, install the backflush hose again and reset the pump to normal settings, then start again.

Unfortunately, even regular backwashing doesn't keep a sand filter running efficiently forever. Eventually, the sand inside the filter container will need to be replaced, although this usually only needs to be replaced every 5 to 7 years. Replacing the sand isn't difficult, but depending on the size of the tank the sand filter is used in, it can be slightly time-consuming.

The backwash is done first, and the pump is turned off when done. Open the pressure valve at the top of the filter cartridge to release the pressure inside the sand filter, then open the drain valve at the bottom of the filter cartridge to release the water inside. Start loosening the bolts that hold the cans together, alternating from side to side to prevent damage to the container from excessive stress on one side.

Remove the top of the canister and scoop out the sand inside the canister. After removing the sand from the filter, inspect the transverse components inside to see if they are excessively loose or damaged. Replace any broken or loose branches, then fill the container halfway with water to help protect them from damage when you start adding sand. Pour or scoop clean sand into the container, filling it to an inch or two from the top; if you're not sure how much sand you should add, consult your pool filter's owner's manual.

After the filter is filled with sand, reconnect the top of the canister and backflush again before starting to pump water into the filter. Check the internal transverse components for excessive looseness or damage. Replace any broken or loose branches, then fill the container halfway with water to help protect them from damage when you start adding sand.

The above describes the working principle of the swimming pool sand filter in detail. If you plan to buy a sand filter, please contact us.

MAYGO is a professional swimming pool filters and accessories supplier. We specialize in professional technical solutions for residential and commercial swimming pools. At present, we have provided swimming pool solutions to thousands of customers in North America, South America, Europe, Australia, etc.