Media filters

Media filters are filters with loose granular media such as sand or grit inside. This media is contained within a shell, often made of plastic or fibreglass and about 1.5m tall.

If there is not much solid material in your water supply, and little manganese or iron (less than about 300 microgrammes per litre of iron), cartridge filters may be enough, and easier to use.

Media filters should be used where there is a significant quantity of sediment in the water or higher concentrations of iron and manganese.

Iron and manganese can cause problems in water supplies because they can:

• have an impact on your water's colour, smell or taste
• stain sanitary fittings and clothing
• block ultra-violet disinfection systems and other vital treatment processes

How media filters work

Media filters work by trapping the solid material suspended in the water. Clean water passes through the filter onto the next stage of treatment.

As the filter gets dirtier, it gets harder to push water through the media and the flow may reduce.

Backwashing - washing the filter by passing water (and sometimes air) back through the media in the opposite direction - means this dirt can be removed, and the filter will be clean.

These filtration systems aren't complicated, but they do need regular backwashing to keep working effectively.

This is best achieved by a timed mechanism that sits on top of the filter vessel, and periodically triggers an automatic backwash by opening and closing the correct valves.

If the media has been used for a number of years, it may need replacing. But this should be left to a specialist contractor.