WATER POLLUTION: FEW QUESTION ABOUT FILTERS
Needless to say, the better filters are more expensive, but a high price is not an unfailing guide to quality, so you need to ask some searching questions:
Does it contain silver? (If not, then it is probably dangerous.)
Is the filter registered with the EPA? What is the registration number? If not EPA registered, then you should ask what quantity of silver leaches into the filtered water. (Ask to see test figures. They should be less than .05 parts per million, which might be expressed as 50 parts per billion, 50 micrograms per litre or 50u,g per litre.)
What percentage removal of chlorine, chlorinated organic chemicals, pesticides and organic solvents does it give? Ask to see test results. (Should be more than 95 per cent for each of these groups. The tests should have been carried out by an independent laboratory.)
How many gallons will the filter process?
What percentage removal can be expected when it is nearing the end of its life? (This is a crucial question – the manufacturer may say the filter is good for 5,000 gallons, but if it is only removing 30 per cent of contaminants after 4,000 gallons you may as well drink tap water. Good filters should still be removing 90 per cent or more at the end of their useful life.)
How much does a replacement filter cost?
Given these figures, you can work out the cost per gallon. Ask whether they are working in British gallons or US gallons, as this will make a difference. (1 British gallon = 1.2 US gallons, so 5,000 US gallons is only 4,160 British gallons.) Bear in mind that the cheapest price per gallon may not be the best in terms of water quality.
The same sort of questions should be asked if you are choosing a filter that combines activated carbon with reverse osmosis (see p311). If they do not include silver, ask about bacteriological control. Filters that work by reverse osmosis alone are not recommended.
None of the above systems remove harmful bacteria, and they are only suitable for use with tap water that has already been chlorinated or otherwise treated by the water authority. All water used for baby feeds should be boiled before use, including bottled or filtered water.
For people who can obtain water directly, from a borehole or spring, there are large-scale devices that kill bacteria as well as removing pollutants and sediment. These are known as water purification systems and are much more expensive, but the water obtained should be of very high quality.
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