FAQ's and Information Leaflets

Water treatment units:

What are they?

A range of water treatment units is advertised for use within the home. These include jug type filters, not connected to the mains supply as well as plumbed-in filtration or softening systems. Manufacturers' claims about the performance of water treatment units may raise concerns about the quality of water supplied by water companies. Some claims suggest that purchase of a water treatment unit will improve water quality.

Common claims include:

• removal of pesticides (activated carbon filters)
• removal of minerals (reverse osmosis)
• removal of taste or odour (activated carbon filters)
• removal of particulate matter or colour (1 micron rated filters)
• removal of hardness (water softeners and reverse osmosis)

Are they necessary?

Your water company has a legal obligation to supply wholesome water that is suitable for all domestic purposes, including drinking, cooking and washing. All public water supplies in England and Wales are safe to drink and there is no need to install additional treatment within the home as a health protection measure.

Virtually all supplies in England and Wales comply with the strict standards prescribed for pesticides in the drinking water regulations. Additional filtration is not required.

Some supplies may contain particulate matter or colour from time to time. While this does not constitute a risk to health, it can be unacceptable to consumers and it may cause discolouration of washing or fittings. Installation of a suitable filter may reduce the problem but the issue should first be raised with the water company. Installation of a filter should be no more than a temporary measure pending the completion of mains cleaning or renovation by the water company.

The most common reason for installing a filter is to improve the taste or odour of water. Activated carbon filters can improve taste and odour but a more cost-effective solution is to store a covered jug of drinking water in the refrigerator. Surveys have shown that most consumers are unable to distinguish chilled tap water from bottled mineral water.

Reverse osmosis (RO) filtration systems remove virtually all dissolved solids, soften the water and produce a waste stream equivalent to 20-30% of the incoming flow. There is also a substantial reduction in pressure through the RO unit. RO may have applications within the home if the consumer is using water for specialist purposes such as photographic processing or hydroponic culture. RO treated water should not be used for potable purposes. Because of the correlation between cardiovascular disease and consumption of naturally soft water the Department of Health has advised that consumption of artificially softened water should be avoided.

Consumers should also be aware that installation of RO could increase water bills by up to one third because of the waste stream. The Water Fittings Regulations require that consumers give notice to their water company of the intention to install a RO system.

The most commonly installed water treatment system is the base exchange softening system. This is an ion exchange process that replaces calcium and magnesium (hardness) with sodium. Ion exchange treatment reduces scaling within hot water systems and improves lather production and efficiency of washing. However, it is a legal obligation, under the Water Fittings Regulations, when installing a softener, to provide a supply of unsoftened water for drinking. The Department of Health has advised that consumption of softened water should be avoided because of its high sodium content, and the correlation between cardiovascular disease and soft water.

If you are buying a water treatment unit?

Ensure that the unit is purchased from a reputable supplier. It may be preferable for the installation to be by a qualified plumber or the supplier's agent. Always adhere to the supplier's advice concerning cleaning or replacement of units, particularly because failure to do so can cause build-up of bacteria. It can be very important to backwash certain units if they have not been in use for several days. Some types include devices to indicate the need for maintenance, or to change the filter.

Advice on water treatment units can be obtained from British Water.