Yet Another Plumbing and Heating engineer


Water Filters

In Britain we are fortunate (compared to most people on our planet) in almost everywhere having clean safe drinking water literally on tap. Although a Martian, observing the flow of bottled water through the checkouts of our supermarkets, corner shops, bars and restaurants, might be forgiven for thinking otherwise. However sanitary and convenient the public supply, many people evidently prefer alternatives. Perhaps this is due to the marketing of bottled water as somehow healthier (despite tests showing that some are quite high in salts, and samples may sometimes have alarmingly high levels of bacteria — no doubt exacerbated by the length of time and warmth of conditions in which they may be transported, stored and displayed before being bought and consumed). Partly maybe it is a foible of human nature: that something we have to pay for is perceived as being better than something cheaper or free.

Another factor may be taste: although water is described in chemistry text-books as odourless and tasteless, chlorinated tap water does taste different from bottled or filtered water. This is the basis of a claim made for water filters: that they remove odours and tastes from tap water. In a, perhaps unfortunate, way this is an acquired taste: once one is accustomed to the taste of un-chlorinated water, tap water can taste quite unpleasant.

The choice then becomes one between bottled water: expensive, bulky and dubious on both health and ecological grounds; or filtered water. And in the latter case between a jug filter: cheap to buy but tedious to use; or a plumbed-in filter: more expensive to install but convenient, cheap and fairly low maintenance to run. (Naturally, as a plumber, I have a plumbed-in filter!)

There are several types, makes and models to choose from:

DIY kit filters with separate filtered water tap

There are a number of competing makes of this type on the market, in the £35-£50 range. They generally comprise

The main problems with this type of kit are:
  1. fitting the tap typically involves drilling a 1/2" hole in a stainless-steel or ceramic sink, which is challenging to the average DIY-er,
  2. the clamp-on connector restricts the flow of water available to the filter to a relative dribble, works only on 15mm copper pipe, and is not particularly robust: it relies on rubber rings to maintain the seal, which are liable to deteriorate and leak when operated (for changing the filter) a number of times.
Better results — much improved flow from the filter, a more convenient isolation valve for changing the filter and more convenient placement of the valve, and more robust connections — can be achieved by installing this sort of filter using 'proper' plumbing fittings rather than the supplied clamp-type connector.

3-way taps

Increasingly widely available are kitchen sink mixer taps with a built-in separate control for dispensing filtered water. Sometimes these are packaged with a water filter kit, otherwise they can be used with a separate filter kit.

Non-charcoal systems

Alternatives to activated charcoal systems include reverse-osmosis and distillation systems. These produce extremely pure water, extremely expensively.

There are also charcoal-based systems with some sorts of silver additives. And devices containing coiled tubes of 'energised' water, wrapped around ordinary plumbing pipes, and so on.

None of these is necessary for the simple task of reducing or removing chlorine and other tastes and odours from ordinary, safe-to-drink, tapwater.


Some charcoal-type filters claim to reduce limescale and scale-based scum on tea. Charcoal filters are not known to have any effect on scale (and it might be a bad thing, from a health point of view, if they did). Limescale treatment is a separate subject.

Well water treatment systems

Treatment of water extracted from private wells (usually where a property doesn't have a mains water supply) is a specialised expertise for which DIY-type water filters are not generally suitable.

Filter lifetime

Charcoal-type filters are generally recommended to be replaced every 6 months or so. This figure is no doubt based on a worst-case estimate of lifetime based on high usage and high pollutant load in the water being filtered, and can probably be safely extended in most cases. The problem is that there is no way of knowing when the filter is exhausted, and it is said that when they are exhausted they may give up batches of their pollutant load to the supposedly clean water being passed out. Whether this is scaremongering by the manufacturers is uncertain, but it seems wise to replace them at approximately the recommended intervals. To this end choosing a make with relatively cheap, readily-available and easily changed refills makes sense.