Working Mechanism of Swimming Pools

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Home renovation

Filters for Pools

Dual sand filters with a unique sand filter media

Dual sand filters with a unique sand filter media

This system’s filters are high-rate sand filters that consist of a large tank made of fiberglass, concrete, or metal, containing a thick bed of special-grade sand with a squarish shape.

During the filtration process, contaminated water from the pool enters the filter via the inlet pipe, which leads to the water distribution head inside the tank. While gravity pulls the water down through the sand, the small sand particles trap any impurities and debris. The filtered water flows out of the tank through the pick-up unit located at the bottom and exits through the outlet pipe.

As time passes, the sand’s collected dirt and debris cause the water flow to slow down. Pressure gauges at the filter inlet and outlet indicate the blockage level inside the pool cleaner’s mind. If the gauge on the inlet pipe shows much greater pressure than the gauge on the outlet pipe, the pool cleaner knows that a lot of debris has accumulated in the sand. This suggests that the filter should be backwashed. To backwash, the pool cleaner adjusts a few valves to redirect the water flow. They shut off the return pipe leading to the pool and open the drainage pipe that leads to the sewer system. They adjust a valve on the filter to connect the pipe from the pump to the outlet pipe and connect the drainage pipe to the inlet pipe. Using this setup, the pump’s water flows up through the sand, dislodging the dirt and debris. The dirty water flows out through the inlet pipe and into the sewer at the top of the filter tank.

The pool cleaner adjusts plumbing valves by turning large handles to redirect the water flow during backwash.

Instead of a sand filter, some pool systems use a diatomaceous earth filter or a cartridge filter. In a diatomaceous earth filter, the pool’s water flows through filter grids coated with diatomaceous earth, a fine powder made from fossilized remains of sea organisms called diatoms. In a cartridge filter, the dirty water passes through a filter made of polyester cloth or corrugated paper. Instead of backwashing, you can remove the filter and hose it off. After a few years (or up to eight years), it’s time to dispose of the old filter and install a new one.

In most regions, the law requires all the water in the pool (or the equivalent volume) to pass through the filter in a certain amount of time, typically between 30 minutes and six hours. For the apartment complex pool shown above, this implies that 167,000 gallons (630,000 liters) of water must pass through the filtering system every six hours!

The pump and filter system are also connected to a well or municipal water line, allowing fresh water to be added to the pool. This is necessary to replace water lost due to evaporation, backwashing, and “splash-out” (water that splashes on the deck or is carried out on people’s bodies and swimwear). When it’s hot outside and there’s a lot of swimming activity, this 167,000-gallon pool can lose 300 gallons (1,100 liters) or more in a day.

Next, we’ll explore the chemicals used in a typical swimming pool.


1. What is the purpose of a swimming pool filter?

A swimming pool filter is an essential part of the pool’s circulation system. It is designed to remove debris, such as leaves, dirt, and bugs, from the water, keeping it clean and clear. The filter works by passing water through a porous material, such as sand or diatomaceous earth, which traps the particles and allows clean water to pass through. Without a filter, the water in the pool would quickly become dirty and unsafe for swimming.

2. How does a swimming pool pump work?

A swimming pool pump is responsible for circulating the water in the pool, ensuring that it is filtered and clean. The pump works by drawing water from the pool through a skimmer and into the pump housing. From there, the water is pushed through the filter and back into the pool through the return jets. The pump is powered by an electric motor and can be controlled by a timer or manual switch.

3. What are the different types of swimming pool heaters?

There are several types of swimming pool heaters available, including gas, electric, solar, and heat pump. Gas heaters are the most common and use propane or natural gas to heat the water quickly. Electric heaters are less expensive to operate but can take longer to heat the water. Solar heaters use energy from the sun to heat the water, making them the most eco-friendly option. Heat pumps are similar to air conditioners and extract heat from the air to warm the water.

4. Why is it important to maintain proper chemical balance in a swimming pool?

Maintaining proper chemical balance in a swimming pool is crucial for the health and safety of swimmers. The chemicals are used to kill bacteria, viruses, and other microorganisms that can cause illness. The most important chemicals to monitor are chlorine, pH, and alkalinity. Chlorine is the primary sanitizer and should be kept at a level of 1-3 parts per million. pH levels should be between 7.2 and 7.8, and alkalinity should be between 80 and 120 parts per million. Failure to maintain proper chemical balance can lead to cloudy water, skin and eye irritation, and even illness.

5. How often should a swimming pool be cleaned?

A swimming pool should be cleaned regularly to keep it in good condition and ensure that the water is safe for swimming. Skimming the surface to remove debris should be done daily, and the filter should be cleaned or backwashed every 1-2 weeks. Brushing the walls and floor of the pool should be done weekly to remove any buildup of algae or other contaminants. Shocking the pool with chlorine once a week or as needed will help to kill any bacteria or viruses that may be present. It is also important to regularly test the water to ensure that chemical levels are within the proper range.

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