Under-sink filtration systems are becoming very popular. A simple system installed under the sink or else close to the sink can make your drinking water so much more palatable. Many parts of the country have water which tastes strongly of chlorine or else tastes earthy. There are a variety of filtration methods available to deal with this. One of the simplest methods is to filter the water intended for the sink only. The rest of the water in the house you don’t worry about. It is a very cost effective of making your mains more palatable.

The plumbing is generally very simple, though there are a variety of methods available, with the water being delivered to either an extra tap on the sink or else a tri-tap which dispenses the regular hot and cold water as well as the filtered water. The same arrangement can also feed an American style fridge-freezer and/or a plumbed-in water dispenser.

The principal choices are 1) full plumbing-in, 2) use of a self-piercing valve, 3) use of a y-piece at an existing plumbing point.

1) Full Plumbing-in means you cut into your copper main and make a permanent connection. The connection should be as close to your cold water tap as is practically possible, and downstream of the isolation valve, usually a ball-o-fix type of valve, which is normally present. The simplest way is to remove about ¾ inch of the 15mm copper pipe and insert an angle stop valve here. This valve is a tee piece with 15mm push fit entries at either end and a single ¼ inch or 3/8 inch branch for the drinking water, and a built in chromium plated ball valve on the branch.

2) Self-piercing valve. There are many self-piercing valves on the market. These clamp onto your 15mm copper main, and in the fitting process, a spike is driven into the main, piercing it and creating a water pathway to your filter. The valve is built into the fitting and enables the water to be released into the filter via flexible tube, once connected. The valve will need to be closed every time you need to change the filter, so you need to give consideration to how easy this will be and whether it would be wise to have an additional isolation valve closer to the filter and in a more easily accessible position. Our shop features two types of self-piercing valve. The Opella valve is a substantial and convenient valve, which is easy to turn on and off providing you can get to it. Our budget self-piercing valve is rudimentary but does the job. It’s comparatively difficult to turn on and off, and is best installed and left permanently open. In that case you would be best to install it along with a separate ¼ inch ball valve at the filter, for when you change filters.

3) Y-piece adaptor. If you have a washing machine connection in a convenient place, this also presents an opportunity to connect your water filter to the mains. Simply attach a Y-piece at that point; and one branch of the Y can feed the washing machine, and the other can feed the water filter. However, if you are connecting an American style fridge freezer this way, do read the manufacturer’s instructions. Many years ago, my big side-by-side fridge freezer packed up, all because we’d sited it next to the washing machine. Over the years the humid air from the washing machine waste-pipe ate away the static condenser on the back. When I finally read the manual I realised I should never have had it so close to the washing machine in the first place.

Our shop features a range of different plumbing kits and individual components. Plumbing Kits

The Filter

The choices available for the type of filter are basically two-fold. 1) level of filtration and 2) physical design of filter.

The first is the level of filtration you need. Chlorine is the basic thing most people want to remove, but water hardness can be an issue alongside the removal of sediment and other undesirable impurities.

Considering the chlorine alone, this is removed by activated carbon. The UK’s water is generally of excellent quality, though occasionally things do go wrong. That is why chlorine is added to mains water. Chlorine is the principal reason why the UK no longer suffers outbreaks of cholera and typhoid. The amount of chlorine in the water varies from place to place. If you can’t taste it then perhaps you don’t need to worry about it. On the other hand, if it bothers you then it’s easy to get rid of. Chlorine is not removed by traditional filters working along the same lines as a sieve, but by the process of adsorbtion.

As the name suggests, Granular Activated Carbon consists of carbon granules. If you shake a GAC filter you can often hear the granules rattling. If these become unevenly distributed within the filter body, then channelling of the water can occur, reducing the effectiveness of the filter. “Carbon block” is made by pulverising the GAC, heating it and then extruding it in block form. The result is a finer, more efficient material, with even greater surface area and with even greater adsorbtion properties than GAC, and without the possibility of channelling.

Besides chlorine and chloramines, the activated carbon used in the filters also removes other volatile or gaseous contaminants, though some people wish to go a lot further than simply removing these contaminants. If you’re among those, and wish to produce water that is very nearly absolutely pure, then you need to consider a Reverse Osmosis System (“RO”). Further information on RO systems may be found here.

The second thing to consider is the physical design of filter, which determines how easy it is to install and remove. Some filters have more than one function in a single filter; others divide these functions into separate stages. Some filters use permanent housings in which different types of filter media may be inserted, whereas others use an integral housing and body. Once used, you throw the whole cartridge away. Of those integral filters, some are generic filters which connect directly to a flexible plastic tube, whereas others have filter body which is detachable from a permanently plumbed filter head and which may be removed by a simple twist (“quick-release”) . Many fridge-freezers use the manufacturer’s own proprietary version of a quick release filter.

The filter which suits most people is a simple in-line Granular Activated Carbon (“GAC”) filter cartridge. It fits directly between your mains and the tap/fridge/dispenser, and once spent is thrown away and replaced. Quick-release versions of the same filter exist to make life easier.

If water hardness is an issue, then you have a choice of masking or removal. The chemical hardness itself can be disguised so that scale tends not to form, or tends to form less. This is often referred to as scale inhibition. This is achieved by passing the water through a polyphosphate bed. In other words, a small container with polyphosphate crystals inside, often built into the filter cartridge itself. The effect is to greatly reduce the tendency to form scale. Note that there is still a tendency towards formation of scale. The other method is more expensive and involves removing the actual scale causing chemicals by passing them through a resin filter. Our basic hardness filters employ polyphosphates and will not entirely remove the tendency towards forming scale. At present we do not offer resin filters on ebay.

Here's a link to our range of under-sink filters: Under-Sink Filtration Systems: Replacement Filters; and here's a link for complete systems: Under-Sink Filtration Systems: Complete Systems

The other important thing you need to consider is the type of tap you want. Our kits contain everything you need to have instant filtered water on tap, from the plumbing kit to an elegant mono-tap for mounting on your sink. If you need a tri-tap to deliver all of your water; cold, hot and filtered; then there is a wide range on the market to choose from, starting at around £60 and going up to around £600 or more. We’re in the process of adding information about taps to our ebay site, so do visit again soon to find out more.

Besides supplying filtered water to a tap, an under-sink system might equally be used to supply water to an American Style Fridge Freezer. You might also consider a plumbed-in water dispenser. This is another range of products entirely. You can choose from cold water on its own or else fizzy water and hot water too. They might be situated on your kitchen counter or concealed alongside the filter, and it’s possible to have an arrangement so that one filter serves more than one appliance.

We hope these notes are useful to you. If you have any questions about the suitability of the items in our shop, or how to fit them, then do feel free to contact us. We’re happy to help.