Water treatment devices are available to disinfect water and kill bacterial and viral pathogens, and to reduce or eliminate a number of other chemical or aesthetic problems. Before investing in a treatment device consult a reputable professional and/or your local Public Health Inspector. It is important to know what the system you are looking at is designed to do. General statements like ”filters and cleans your water”  may not give you enough information.



Disinfection systems are designed to destroy pathogens – the bacteria and viruses that can cause illness. Most systems do not remove other contaminants from the water. There are a variety of options available offering different features and having different disadvantages. The following information is intended to help you decide which is right for you.


Ultraviolet Light (UV)

This is the most common form of domestic system. The systems destroy microorganisms by exposing them to ultra violet radiation. The systems tend to be reasonably cost effective, are easy to install and can treat the whole water system. They require limited maintenance, but the UV lamp should be checked and cleaned periodically and replaced where necessary. UV does not provide any residual disinfection which means that each property on a shared water system should have its own UV device. Cloudy, turbid, highly contaminated, or high iron water may not be effectively treated without suitable pretreatment (such as a filter system).



The most common system in use in larger systems (sometimes in combination with a UV system). A Chlorinator adds a chlorine solution through an injector mechanism to kill microorganisms. As the system provides residual disinfection it can treat more complicated water systems with buried piping or multiple buildings. The chlorine residual can be tested to ensure correct disinfection. Chlorinators tend to be more expensive than UV, require more maintenance and a more knowledgeable operator. Chlorine also requires at least 15 minutes contact time (CT) which in turn requires the water system to be engineered to include a certain amount of water storage. When water containing a lot of organic material is treated with chlorine, undesirable or even harmful by-products can be produced.


Reverse Osmosis

Sometimes found in homes and cottages, Reverse Osmosis (RO) systems force water through a semi-permeable membrane to remove bacteria. The systems remove many metals, minerals salts, chemicals and unpleasant tastes but the membranes may also be fine enough to remove pathogens – check with the manufacturer or supplier. Most systems are reasonably cost effective and are easy to install but can only treat small amounts of water. As such they tend to be a “under counter” system supplying treated water to a single faucet. Systems are available that are large enough to treat the water supply for the whole house, but these are expensive and may require more management. In addition RO units produce waste water meaning that your overall water consumption will increase. Pretreatment may be necessary to protect the membrane filters which is delicate and must be intact for the system to work safely, although most modern systems include the pretreatment.  



Not technically a disinfection device. The basic cartridge filter is available in different sizes and ratings. Filters are rated by how large the particles they let through are – a 20 micron filter will let through particles up to 20 microns whereas a 5 micron filter will only let through smaller particles up to 5 microns in size. Disinfection systems will operate better with, and may require a pre-filter.


Other Devices

As newer technology becomes more affordable systems such as ozonators (that produce ozone to destroy pathogens) may become cost effective. For camping and other “off the grid” uses, ceramic and other advanced filters are fine enough to remove pathogenic bacteria (but not usually viruses).




Chemicals such as iron, manganese and calcium hardness (to name a few) can impart disagreeable taste and odors. Some chemicals can cause economic concerns as well: for instance very hard water will use more soap or laundry detergent and can shorten the life of equipment such as dishwashers.


Activated Carbon or Charcoal Filters

Designed to remove chlorine, odor and unpleasant taste. Are relatively inexpensive and easy to install and require no power to operate. They should only be used on disinfected or bacterially safe water and even then bacterial counts may ultimately increase in the water passing through the filters. For this reason charcoal filters must be changed often.


Water Softener

Water softeners use ion exchange (calcium to sodium) to reduce the amount of calcium that causes hard water, they may also help to reduce other nuisance odors and tastes. They are moderately expensive to install and maintain, but may reduce maintenance and replacement costs of other goods such as dishwashers. Softened water increases the sodium in the diet of those who consume it and is not recommended for consumption – particularly for those on a sodium restricted diet. Backwash from softeners should typically not discharge into a private sewage system (septic tank).


Special Filters

Filters are available that are designed to remove specific pollutants. These systems should be installed by a knowledgeable and competent person with experience in water treatment


The following website is an excellent source of more information on this subject:




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