Due to the amount of times I get asked this question, I have agreed to (finally!) put it into one of our regular blog posts. I really do get asked this question almost every day!
Firstly, let me address why I think I am qualified to answer this question. I am the founder and general manager of Osmio Water. We have been supplying water purification equipment for around 5 years and in that time I have personally used and tested a large number of systems from a wide variety of manufacturers. I have used every single product in our extensive range and also test the many samples we are sent from keen manufacturers around the world wanting us to range their products. We also deal with a large number of clients across the United Kingdom and Europe who have private water supplies so we know exactly what our systems are capable of doing.
Due to the dissatisfaction with tap water or the high cost, PET plastics and ethics of the bottled water industry, many people seek out the logical solution which is a water filter. As with many things however, water filters are not made equal! So which is the best water filter?
There are broadly two types of water filter:
1) Inline Filters - These are the most commonly used kinds. You will find then on Fridges, Jug filters, Under-sink filters and anyway else. Water passes through the filter and immediately out again. 100% of the water goes and and 100% (minus some dissolved gases) goes out - so basically the entire volume of water is treated. They can contain a variety of different filtration media from carbon, to phosphates, to ceramic.
2) Reverse Osmosis Filter Systems - These use inline pre-filters and then the water is pushed through a fine membrane. The membrane is extremely fine and is capable of stopping many contaminants including dissolved solids. The rate of purification is quite slow, the pace of a fast drip which slowly fills a small storage tank. Once the tank is full the system shuts off. The system produces waste water as not all the water is capable of passing through the membrane. The waste water contains all the material that cannot pass through and this is often sent to the drain. Reverse Osmosis is often criticized for the waste water production. Sometimes people refer to it as "dead water" or unhealthy.
We often get asked about water ionizers which I will discuss in detail on a separate blog post. Ionisers are capable of raising the pH of water to very high levels. In the UK the water regulations state that the pH should be between 6.5 and 9.5. Anything over 9.5 has the potential to start interfering the stomach acids and digestion. Your stomach has a pH of 2.0 and water ionizers have the potential to raise water pH to between 11.0 and 15.0. This will therefore neutralise stomach acids which reduce the stomach's capability to kill microbes.
The best systems we currently (at the time of writing this September 2014) are the Puricom ZIP Portable Alkaline Reverse Osmosis System and the Pure-Pro Alkaline Under sink Reverse Osmosis System.
Why are these the best water filters?
Both these systems produce ultra-pure water which then has mild alkaline conditioning to raise pH levels to around 8.5 to 9.5 levels whilst keeping a low level of TDS to around 40 ppm reducing or effectively removing the largest range of contaminants than any inline systems are capable of.
The only downside to any reverse osmosis system is the waste water produced. It is physically impossible to remove a very high level of dissolved solids and gases without separating pure water from concentrated water, which is exactly what reverse osmosis does. The Puricom ZIP, however, has a fantastic waste to pure water ratio due to a patented waste recirculation system. The unit ends up producing exactly 50% pure water to 50% waste, but the waste is not connected to the drain but kept in the supply pitcher, enabling you to use it for gardening or cleaning etc. In contrast the Pure-Pro system is a fully plumbed in system which benefits from greater convenience but inevitably produces a larger waste ratio which is usually connected to the drain, but not always! Recently we had a customer who built and eco-home and has the RO waste connected to a garden water butt, with the help of 15 metres of extra tubing! Easily done and a great innovation!
So in short both systems produce the type of water you want - highly pure (thousands of times better than any inline or gravity system) but with perfect pH conditioning. Pure RO water without any conditioning is less than 6.5 pH and can be as low as 5.0.
Let me know your thoughts!