How Does A Swimming Pool Filtration System Work?

Underwater Pool Leak Detection As Swimming Pool Leak Detection Experts we aim to write about swimming pools, filtration systems and how pool leak detection works in laymans terms, helping you to carry out some DIY pool leak tests and gain a deeper understanding of your swimming pool system.

All swimming pools are constructed and operated on the same principle.

In other words, regardless of the shape, size, and additional features; the functioning of all pools is basically similar. They all use a combination of chemical treatment and filtration to keep the water clean and healthy at all times.

In this post, we’ll be looking at the filtration system and how it works. Usually, the water filter is used to keep algae and other hazardous contaminants at bay.

Here we go:


  • This is the most important part of the pool system. The pump has an electric motor that spins the impeller inside the casing and carries the water from the drains. Water passes through the skimmers and flows to the wet end section of the pool pump.
  • The wet end section of the pump includes a shaft seal, strainer lid, diffuser, strainer bucket, impeller, and strainer ring. The water goes through the pump and out through the pump discharge, to the filter.


  • During the pool filtration process, the dirty water from the pool goes through the inlet pipe of the filter to the distribution head located in the tank.
  • Depending on the type of filter you have, as the gravity pulls the water down, either cartridge, sand or diatomaceous earth traps the debris and dirt.
  • The pressure gauges at the outlet and inlet indicate the level of blockage in the filter. If the gauge reads much higher pressure in the inlet compared to the outlet, it means there’s a lot of dirt and debris.
  • There is a need for regular backwashing or cleaning the filter cartridges.

You can’t have a swimming pool without a pool filter. Filters free the water from visible debris and invisible contaminants. These include micro-organisms from infected swimmers, disease-causing pathogens, tiny insects, food particles, saliva, sweat, urine, fecal matter, among other things.

Pool filters can also hinder the growth of algae and bacteria.

Here are the major types of pool filters

Swimming Pool Leak diver There are three main types of pool filters, namely; cartridge, Sand, and Diatomaceous Earth (DE). Here is a description of each:

Cartridge filters

These are commonly used for above-ground pools. They are the easiest to use and maintain. They filter by holding dirt particles and debris in the cartridge, before passing the clean water back into the swimming pool.

You can open up the cartridge when it’s too dirty, cleanse it with a hose and reuse it. However, it’s important to replace the cartridge periodically, at least once per year.

Diatomaceous Earth (DE) filters

Cover the filter with DE. The DE gets rid of the tiniest dirt particles, as small as three microns (too tiny for the naked eye to see). DE system ensures that the water is super clean because it involves manual cleaning and backwashing. You need to add the amount of DE in each filtering session.

Using the DE filter is easy and straightforward; put the DE powder to the pool filter, this powder contains microscopic diatom skeletons, a form of algae. In a sponge-like effect, the powder absorbs debris and dirt particles from the water passing through the filter. The skimmer box is used to sift out the dirt and debris.

Sand filters

Sand filters function by passing dirt water through a sand filtration system. The particles are trapped in the sand, and clean water returns to the pool.

When the sand gets dirty, it calls for a backwash. Backwash means running the filter in reverse to remove excess debris.

You can recycle the same sand for at least five years. You can also use glass media in place of sand. Glass media filters filter better and require less backwashing and serves for more years.

  • Parts of a sand filter

    • Corrosion-proof hollow tank- the main body that holds sand and other parts
    • Specially graded sand as a media that leads to the tank
    • An integral top diffuser that allows for the even distribution of water
    • Slotted lateral pipes- balance the flow of sand
    • Laterals-hold back sand allowing water to pass through
    • Corrosion-proof bases that support the tank
    • Drain plug for easy draining
    • Multiport valve is found at the top of the tank with a cramp and an o-ring that protects the valve on the filter.

Importance of balancing the pool water

The Pool filtration system plays a vital role in keeping your swimming pool clean and healthy. A healthy chemical balance benefits everyone; swimmers, the pool, and even the equipment used therein. An untreated or poorly treated pool is a haven for pathogens and other disease-infested micro-organisms.

Furthermore, incorrect chemical balance can destroy other parts of your swimming pool, including the filters; it also causes the water to turn grey and cloudy, irritating your eyes and skin.

Pool leakages

Pool leaks are common anywhere in or outside the pool. Before looking for a leak in your swimming pool, ensure you have checked the whole filter system including the heater, filter, pump, chlorinator, etc.

Leaks can also occur in an in-ground pool from cracked underground piping. You must also determine whether you are losing water through leakages of evaporation.

In most cases, the best thing would be for you to contact a professional leak detection company. Only such has the equipment and skills to quickly pinpoint the leak in a non invasive manner.

Filtration System Specialists Lookout for these Signs of pool leakage

  • Extraordinary discoloration of water or algae growth
  • Abnormal consumption of water
  • Varying chemical consumption
  • Failing or loose tiles
  • Cracking of the swimming pool cement deck
  • The pool settling into the ground
  • Water corrosion around the pipes or at the pump
  • Soggy soil at the underground plumbing lines


Why you should NEVER ignore a pool leakage

Pool leakages are both an inconvenience and a potential hazard. Water escaping from the pool system can easily start accumulating in areas that it shouldn’t.

For instance, chlorinated water can spill off and damage metal components around the pool structure such as rebar covering, shells of the concrete swimming pool and galvanized steel of a vinyl liner pool walls.

Besides, the leaking water can carve through the ground of the pool if left unattended. Over an extended period, the water washes away cement strips from the concrete, leaving only gravel and sand behind. This damages the pool basement.

Like we’ve mentioned, pool leaks are both an inconvenience and a potential hazard. The earlier you get them fixed, the better.

We are your go to company for all your pool leak problems.

We’re professional; we can detect and fix all manner of pool leaks in your home or commercial premises.

Our team of engineers and technicians has state-of-the-art equipment to detect pool leakages without digging the pool area. In some cases, we can repair leakages without excavation.

Call us on 0800 731 3843 to discuss the problem with your filtration system or swimming pool.

Adrian Morgan

Adrian Morgan CIPHE RP RHP is the founder & Managing Director of ADI Pro Leak Ltd. Adrian is also the Head Plumbing, Heating & Leak Detection engineer at ADI Leak Detection.

Adrian CIPHE RP RHP is proud to be registered with the Chartered Institute of Plumbing & Heating Engineering, a Registered Plumber and a Registered Heating Professional.