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Filtering out the facts

11 November 2011 swimart

Filtering out the facts

Filtering out the facts

The different types of pool filters

Whilst there's a lot of confusion about what type of filter is best for your pool, the one thing that can't be disputed is a filter's role. Filters 'clean' the pool's water by passing it through some form of filter medium and returning it to the pool in pristine condition. So what type of filters are there?

SAND FILTERS

Described by some as the bullet proof filter, sand filters are the most commonly used filter for both domestic and commercial pools. Pool water passes through a tank filled with finely graded sand. You could say it operates somewhat like an espresso machine. As water passes through, the impurities attach themselves to the grains of sand. The larger particles are trapped at the surface of the sand bed and the finest particles are collected deep inside the bed where the grains are more tightly packed.

One of the benefits of the sand filter is its simplicity. When the bed of sand is clogged with dirt, the pressure inside will register on a gauge, which indicates the need to flush or backwash the filter. Switch off the pump and turn the valve to 'backwash', which will reverse the water flow and send the unwanted particles down the waste line. The water should be clear after a minute or so.

The sand in the filter will normally need changing approximately every five years, although this will depend on factors such as pool usage and size.

HINT: Do you know when you last changed the sand in your filter? Whilst the filter will still work it certainly won't be as effective!

DIATOMACEOUS EARTH (DE) FILTERS
Diatomaceous Earth is a powder made up from finely crushed coral-like rock (fossilised exoskeletons of tiny diatoms). Each grain has microscopic holes running through it to trap even the finest particles. It's added to the filter by mixing with water in a bucket and tipping the slurry into the skimmer box (with the pump running). It is sucked into the filter, forming a cake on the outside of the pad. As water passes through the pad it must also pass through the cake of DE, where filtering takes place. The DE cake drops from the pad when the pump is stopped, then reforms again when the pump is started.

As the grains of DE are so fine, this type of filter has superior filtration qualities, and can remove particles down to approximately five microns in size. When the pressure rises it is an indication that the DE cake is clogged and the filter needs backwashing.

Backwashing is the same as it is for sand filters, however the DE material is also flushed away and a new slurry needs to be added after the backwashing is complete. For the system to operate efficiently, the septums (in the filter) will also need to be removed and hosed down once or twice a year.

CARTRIDGE FILTERS

Cartridge filters in some way incorporate the benefits of both sand and diatomaceous earth. Folded into the tank like a concertina, the filter material has quite a large surface area, which means the filter cycle is increased.

Unlike other filters, there's no provision for backwashing. When the cartridge is clogged, it must be removed for cleaning. Generally this entails hosing it off, but those used in a heated pool or spa may need to be soaked in a cleaning solution. One of the advantages of the cartridge filter is that the method of cleaning makes it ideal for use in unsewered areas, or where disposal of waste water is a problem. The filtering ability of the cartridge filter is somewhere between sand and diatomaceous earth and will remove particles down to approximately 8-10 microns in size.

 

 

Introducing the new filter media – glass!
Waterco Ltd has extended its recently launched EnviroPro range with the launch of a new generation of superior pool water filter media, Waterco's Glass Beads. Manufactured from 100% virgin glass, Waterco's Glass Beads offer much finer filtration than other alternatives and are therefore capable of providing outstanding water purity and clarity (filtration below 3 microns). They also require 20 per cent less water for backwashing compared to sand.

Ultimate water purity
"Whereas other filter media may contain different contaminants– Waterco's Glass Beads are manufactured from 100% virgin glass and are chemically inert for the ultimate water purity," says Waterco group marketing director, Bryan Goh. "In fact, Waterco's Glass Beads have been independently lab tested for leaching contaminants and found to be well within Australian Drinking Water Guidelines."

At only 0.6mm by 0.8mm in size, the narrow particle size of the Glass Beads enables in-depth superior filtration. The spherical shape also results in low friction levels, also reducing the need to backwash and saving pool owners both time and precious water.

Ultimate safety
Not only that, Glass Beads are safe to handle and safe to service, explains Goh: "Unlike crushed glass, Glass Beads are spherical and do not have sharp edges, making them really safe to use. And if there's ever a failure of the filter's laterals and glass beads flow into the swimming pool, they pose no risk of injury to swimmers."

Ultimate time saving
Glass beads are also easy to install, enabling a rapid start up of the media filter. Plus its high purity means very little backwashing is required to cleanse the filter media prior to commissioning the filter.

 

 

A godsend for pool owners
If you're looking to save thousands of litres of water a year and reduce filter maintenance, then look no further than the award-winning MultiCyclone – the revolutionary centrifugal pre-filtration device being used in residential and commercial swimming pools around the world.

The MultiCyclone works on the basis of centrifugal water filtration. There are no moving parts to wear and tear, and no filter media to clean or replace. The device spins sediment down to the sediment sump, while the cleansed water spirals upwards. The MultiCyclone is cleaned by simply opening its purge valve.

Simply put, the pool water ends up cleaner with less upkeep. The MultiCyclone gathers dirt that would normally go into the filter, and drains it out. In doing so, this cuts 80 per cent of the dirt that clogs your filter, eliminates backwash by up to 40 per cent – and extends the life of your filter. It only takes 15 litres of water to flush the MultiCyclone, which saves you time and money.

The next generation – the MultiCyclone Plus – takes the technology even further. It's a compact, all-in-one pre-filtration and filtration unit, combining all of the revolutionary features of its predecessor with an inbuilt cartridge filter. And the streamlined design means the entire pool filtration system can be installed vertically, atop a standard pool pump.

The MultiCyclone Plus uses the most advanced hydro cyclone technology to reduce the footprint of the filtration system. The reduced workload of the filter cartridge greatly improves pool circulation and allows vacuuming of the pool without overburdening the filter cartridge. It means the MultiCyclone Plus is a safe and cost effective easy way to save between 7,000 and 10,000 litres of pool water per year compared with sand filtration systems.