How Does a Swimming Pool Filter Work?

A swimming pool is a significant investment, and so you want to ensure it’s well-maintained and safe to use all year round. The filter system of the pool is crucial in keeping the water clean with minimal human intervention.

At Paramount Pools, we believe understanding the inner workings of the filtration process will help owners get the most out of their system and keep pool water clean all year round.

This article answers the questions, How exactly do swimming pool filters work, and What different types of systems are there?

The Role of a Swimming Pool Filter System

Your swimming pool filter system’s primary job is to remove dirt, debris, and microscopic particles from the water. While chemicals like chlorine or bromine sanitise the water by neutralising bacteria and algae, the swimming pool pump and filter physically removes suspended solids. Without an effective filtration system, pool water can quickly become cloudy with dirt and potentially filled with larger debris, all of which makes for an unpleasant swimming experience.

The Filtration Cycle Explained

A typical swimming pool filtration system works in a closed-loop cycle:

Water Intake: Water is drawn from the pool towards the filter units via the skimmers and main drains.
Pump Operation: The pump and filter for swimming pool systems work together to drive the water through the filtration process.
Filtration: Water passes through the filter, which traps unwanted debris and particulates.
Return Flow: The now-clean water is returned to the pool via return jets.

This cycle runs continuously while the filter system is active, ensuring the pool water remains clean and safe for swimmers at all times.

The Importance of Flow Rate in Filter Systems

A key factor in any swimming pool filter system is the flow rate (how much water passes through the filter per minute). If water flows too quickly through the system, debris might not have time to get trapped, and water might not be adequately cleaned before it’s returned to the pool. Equally, a low flow rate can lead to blockages or an ineffective system.

An optimal flow rate ensures effective filtration without overloading the system. At Paramount Pools, we carefully calculate the correct pump and filter for swimming pool installations based on your pool’s volume and usage, ensuring maximum performance and energy efficiency.

Types of Swimming Pool Filter Systems

There are several types of swimming pool filter systems, each with its own method of cleaning pool water:

1. Sand Filters

How They Work: Water is forced through a bed of specially graded sand, which traps dirt and particles as small as 20-40 microns. Dirty pool water enters through the inlet pipe, leading to the water distribution head. Gravity then pulls the water downwards, through the sand, before exiting out the outlet pipe at the bottom of the filter unit.
Maintenance: Requires backwashing (reversing water flow) periodically to clean the sand. The shell is typically made from metal, fibreglass, or concrete, which may require infrequent maintenance.
Pros: Simple, durable, and relatively low-cost.
Cons: Slightly less effective at filtering finer particles compared to other systems.

2. Cartridge Filters

How They Work: Water flows through a pleated polyester cartridge that traps debris down to 10-15 microns. The cleaned water is then returned to the pool with jets.
Maintenance: Cartridges need to be removed and rinsed regularly. These will eventually need to be replaced.
Pros: Energy-efficient, fine filtration, no backwashing needed, ideal for smaller pools and spas.
Cons: Cartridges wear out over time and must be replaced.

3. Diatomaceous Earth (DE) Filters

How They Work: DE is a porous powder which coats the inside of the filter. As the pool water passes through this powder, it can capture particles as small as 3-5 microns. There are many elements within the filter which become coated in DE powder, allowing the water to go through multiple cleans as it passes through the unit.
Maintenance: Requires backwashing and periodic recoating with DE powder to ensure effectiveness.
Pros: Offers the finest level of filtration, quick treatment of algae and bacteria.
Cons: More complex maintenance process, cost of replacement DE.

Commercial Filter Tanks

SMDD Commercial Filter

This Micron SMDD filter has an extremely deep bed (1.2m) for greater dirt capacity. These filters can be adapted to a wide range of applications due to their ease of installation, including hotels, outdoor public pools, water features, aquariums, and to support industrial processes. Key features include:

Pressure rating options of 2.5, 4, 6, and 8 BAR.
Ultra-smooth Bobbin finish.
PVC flanged connections.
NSF approved reinforced fibreglass inner shell.
Nozzle plate version (SPDD).
Option for vinyl ester resin coating.

SMD Commercial Filter

As part of the Waterco Micron commercial fiberglass filter range, the SMD model is manufactured from the highest grade non-corrosive materials. It’s available in top, side, and horizontal mount configurations so it can fit various applications. Key features include:

1m deep bed.
Available in 2.5, 4, 6, and 8 BAR pressure ratings.
Ultra-smooth Bobbin finish.
Quick connect unions, up to and including SMD 2000.
Large, stable base.
Options for nozzle plate version and vinyl ester coating.

Domestic Filter Tanks

SM Bobbin Wound Top Mount Filter

All our domestic pool filter tanks come with a 10-year warranty to protect your investment. Key features include:

2.5 BAR max working pressure.
UV-resistant construction.
Multiport valve with 1.5” and 50mm socket unions.
Internal air bleed system.
Maximised water flow through hydraulically balanced laterals.

Monobloc Sand Filter Combination

The combination of a Thermoplastic Filter and Aquamite pump achieves a 2.5 BAR pressure rating. Ideal for both residential pools and commercial facilities. Key features include:

250mm bed depth.
Built-in pump.
Optional six-position multiport valve.
Sight glass and quick connect half unions.
8, 10, and 14㎥ / hr flow options.
Size of the tank can be scaled to the demands of the pool.

Micron Filament Wound Sand Filter

This high-quality fibreglass filter is suited to respond to constant fluctuations in water pressure. Residential installations come with a 10-year warranty as a testament to the reliability of this filter range. Key features include:

Internal air bleed system.
8” removable clear lid.
2.5 BAR max working pressure.
Hydraulically balanced laterals for maximised water flow and filtration.
High resistance to wear and tear.
UV resistant.

Supporting Components

While the swimming pool filter is the part that performs most of the cleaning for the water, there are a variety of components that contribute to the filtration system as a whole. This includes:

Skimmers: Collect floating debris like leaves, hair, and twigs from the surface of the water before they sink. Pool skimmers are usually built into the side of the installation just below the water line.
Pumps: Power water movement through the filter system. Where the skimmers and main pool drain serve as openings that pull water through, the pump creates a continuous motion. This circulation is essential to prevent water from becoming stagnant and accumulating dirt.
Return Jets: Circulate clean, filtered water back into the pool.
Valves: Direct and control water flow during normal operation and maintenance. Valves are installed at various points throughout the pool plumbing. They also help adjust water pressure and prevent water from entering certain parts of the system when necessary.

Case Study – Aqua Platinum Superior Pool Filtration

We were tasked with improving the water quality and sustainability of a fully tiled 125㎥ mosaic swimming pool and 30㎥ vitality pool. Both were designed and built by the award-winning Aqua Platinum Projects. On top of this, the luxury property on London’s Strand was part of Berkeley Group Holdings and so required only the highest quality filtration solution.

Two premium Waterco SMD1200 Micron Commercial Fibreglass Filters and two Hydrostar 4HP pumps were installed in the vitality pool, and two SMD1050 Micron Commercial Fibreglass Filters and two Hydrostar pumps for the main circulation jets. The water features were supplied with three Hydrostorm 1HP Pumps.

Maintenance Tips for Peak Filter Performance

You must keep your swimming pool filter system operating efficiently to protect your pool throughout the year. We advise performing the following filter maintenance:

Clean or backwash your filter as recommended for your type.
Regularly check pressure gauges for signs of clogging.
Maintain proper pool water chemistry to prevent scale build-up and algae.
Schedule professional inspections to catch early signs of wear or malfunction.

Conclusion

Your swimming pool filter system plays a vital role in maintaining sparkling, safe water. Whether you have a sand, cartridge, or DE filter, understanding how it works can help you better care for your investment.

At Paramount Pools, we offer expert advice, high-quality equipment, and professional installation to ensure your pump and filter for swimming pool systems perform flawlessly.

Get in touch if you have any questions about our range of filtration solutions, whether that’s pumps, swim jets, skimmer pools, or the filters themselves. Our dealers operate across the UK, so installation is never far away.