Requirement of quality and unpleasant taste explain this disaffection for tap water and the fact that one day or another one may consider a household filtration device.

There are a large number of models among the simplest versions that are part of water bottles, water jugs or counter top dispensers. Then there are more complex reverse osmosis units, and electric filters that are installed under your sink or outside to suit the whole house. 

Filter jugs, made by many brands, are economical to buy and are small and practical. In use, they remove the taste of chlorine very well, but this is not a feat … even without a filter, we get rid of it just as much by filling a pitcher in advance to let the water ventilate.
They also eliminate part of the pesticides, heavy metals (lead, copper, zinc …) and nitrates, provided that the filter is changed as soon as it is expired, after a period which varies depending on the nitrate content of the water. The best way to check this is to buy test strips.

These decanters have a capacity of 2 l on average (1.3 l of filtered water). Compared to fixed installations, the flow is very limited and the storage low, but to serve at the table or prepare tea or coffee, it is sufficient. A cartridge can treat an average of 100 to 150 l of water, and manufacturers recommend replacing it every one to three months. 

The main defect of these decanters is the risk of bacterial infection due to contact of water (and often the filter) with air, especially since bacteria can also develop on the filter itself. You must therefore take care to close the cover, never keep filtered water for more than a few hours (preferably in the refrigerator), never leave the cartridge in the ambient air and, above all, replace it very regularly. Once saturated, resins and activated carbon may no longer perform their function and they “release” into the water all the impurities they had retained. In this respect, a saturation indicator indexed on the actual quantity of water treated is preferable to a simple date, which does not take into account the flow rate. The best way would be to have data not based on the volume filtered but on the mass of pollutants retained.

Average around 6 to 7 dollars for a cartridge, or 70 dollars on average per year. However, there are models to fill yourself with a bag of activated carbon. More economical filters, $26 for six bags for the Alpatec brand, for example.

The devices to be adapted to the tap use the same type of filtration as the carafes, but the service life of the filter cartridges is much longer, 700 to 2,000 l depending on the model, which corresponds to a change every three or four months. The strong point of the system is the presence of a saturation indicator on the cartridge, often coupled with a filtration stop as soon as it needs to be replaced. These materials can be disengaged at any time: dishes or floor maintenance that does not need purified water. In everyday life, it’s more or less practical, and the device is rather bulky
Remember especially that it is to be avoided if the sink is located in a sunny area, because the cartridges are sensitive to heat. These cost around $60 to $80 for the device itself, but $20 to $50 for refills, an annual cost of use of $80 to $150.

Filter taps are a more attractive option, both practical and aesthetic. They only reveal a small spout at the sink or, better, couple the filtration system to a mixer or a mixer (from $300). The cartridge (30 to 40 cm size) is installed under the sink and is connected to the cold water supply via a tee which allows simultaneous supply of cold water to a mixer tap (or a mixer) and the filtered. The latter is never in contact with the ambient air. They therefore require less hygienic precautions. Regarding filtration, it all depends on the manufacturers. Franke provided his devices with a ceramic filter (against pesticides, heavy metals, bacteria) doubled with activated carbon (for chlorine and all that is unpleasant odours or tastes). If nitrates are also to be treated, a second, specific, must be installed upstream.

With Jado, Ideal Standard, Jacob Delafon or Kinetico, the operating principle remains almost the same, namely an activated carbon filter which takes care of chlorine, unpleasant tastes and odours, lead, but not nitrates.

Franke or Jacob Delafon recommend changing the filter every six months, as a precaution, while one advertises 3,500 l of treated water, and the other 7,500 l. Jacob Delafon has a customer service department which regularly sends you letters to remind you of the order (from the date of purchase). For Franke, a significant reduction in flow is a sufficient indication of saturation.

As for Jado or Ideal Standard, the filters (planned for around 1,000 l) are designed to last three months, whether or not they are saturated, because in the eyes of these manufacturers, the carbon is no longer active after this period. Kinetico equips its filter with a control system which stops filtration when the 1,800 l provided is drawn. An even safer method

Activated charcoal cartridges cost around $30, ceramic cartridges $100, and up to $230 for a specific anti-nitrates cartridge. The annual cost of use, following the manufacturers’ instructions, is around $120 to $140, a little more with Franke equipment.

Reverse osmosis is the most reliable technique for obtaining “pure” water. The manufacturers’ instructions (Kinetico, Permo, Aquadomo) indicate a production of filtered water of up to 150 l per day, or even 200 l, for the largest units. But these are maximum data, recorded under good conditions of use. That is to say at an ideal water temperature of 10-15 ° C, with a pressure of at least 2.4 bars, and taking into account the amount of substances present in the water. These three factors influence the flow rate, which can be only 30 to 40 l in the end, a sufficient volume for everyday use, since only water intended for food consumption (drink, cooking) is treated. Intensive use of these devices would be too expensive, because to obtain 1 l of purified water, they consume between 3 and 5 l approximately.

Osmosis units are usually placed under the sink. However, there are more compact ones that can be installed on the worktop. Their operating principle is correct, and they are worth less ($ 600 instead of $2,000). We still lack hindsight to know if their lifespan will equal that of the classic versions, which is at least ten years.

The device requires regular maintenance (change of filters) which is generally entrusted to the installer. An intervention which costs $150-200 per year (except with the small models which you change the filters yourself). And in order not to tire the equipment too much, adding a softener upstream is strongly recommended in regions where the water is very hard. In short, equipment to be preferred where the risks are real. Elsewhere, it is a luxury.