From the Vault: Home water treatment and the sceptical consumer

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Kim N
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The New Zealand Skeptics
Home water treatment systems are often promoted on the basis of the purported health (rather than aesthetic) benefits of using them. This is particularly in relation to urban drinking water given the full treatment — coagulation, sedimentation, filtration and disinfection — where such claims usually constitute misleading advertising. In this review I will focus on a number of misconceptions about the health benefits of water treatment, examining each assertion in its wider context. The ensuing discussion applies less to rural water supplies, where valid reasons often exist for use of treatments — eg removing nitrate or protecting against giardia. Recently it has been emphasised that water purification systems require a degree of periodic maintenance which the modern householder is not very good at delivering. Over time, poorly maintained systems can become health hazards in their own right, as bacteria start to flourish, and contaminants previously retained may leach back into the water. This issue has already been exposed to the full glare of the New Zealand media’s 40-watt bulb, and I will side-step it by assuming (in what follows) that the treatment systems involved always function according to ideal specifications.
New Zealand Skeptic, 2018, (Number 121, Summer 2018), pp. 20 - 23