I live in a hard water area and so filter my water using a Brita filter for coffee. In the UK for Brita filters there is a company called Phox who make a refillable cartridge, with their advertising suggesting that using their refillable cartridge is more environmentally friendly than Brita. Their claim that the water is more environmentally friendly seems obvious at first but given that you have to throw out the filter material each month, it’s not clear whether this is more environmentally friendly than Brita’s recycling scheme where they recycle the filter material.

So I have been researching two things. The first is which is better environmentally and the second is whether the Phox or Brita filter is better at filtering. I haven’t got very far with the first one since you need to compare the environmental costs of throwing out the filter material and compare that with the environmental costs of producing and recycling the filter cartridges each time. I’d be interested if anyone has any insights. I think that the Phox filters are probably better for the environment but when using them you personally generate some waste, where as with the Brita filter recycling scheme you give the filters back to them and the environmental costs is sort of on them rather than you.

The question of which is better for filtering is much easier to answer and was very surprising. To test this I bought some water hardness test strips, a TDS meter and a pH meter and decided to measure the difference between the water in and water out when using a fresh filter. For both the Brita and the Phox filter I used the filters recommended for hard water: Brita’s limescale expert and Phox’s softener pack.

I recently made a youtube video talking about the tests and the results.

For the water hardness, both filters made the water indistinguishable from distilled water when using the water hardness test strips, so I think its fair to assume that the water hardness goes to zero with a fresh filter. For coffee this is actually not what you want, and ideally would have a certain level of hardness. The speciality coffee association (sca) recommends a water hardness of 112ppm and so if the input tap water is higher than this you can achieve this by mixing some of the tap water with the filtered water. This is what is done in filters like the Peak water filter where they have a built in bypass. If your water hardness is x ppm, with x > 112, then having a solution of 112 / x * 100 % tap water and the rest filtered water will get the correct hardness level (assuming no reactions happen when you mix the waters together). I think this explains why sometimes with coffee you can have good coffee beans that taste great but which then don’t taste as good after a while. To try and fix this you then replace your water filter but then it still doesn’t taste as good as before – initially your half way depleted filter was producing water of an ideal hardness, but the old and new filters are producing water that is either too hard or too soft. The best thing to do is to start off with the calculated ratio and then to decrease the percentage of tap water as your filter depletes. After a month of use, both filters were producing water that was the same level of hardness as the tap water. I’m not sure whether the hardness increases linearly over time or whether the filter keeps producing water of 0 hardness for a while and then suddenly stops reducing the hardness at all. I assume the former is more likely, but don’t know. I will have to do more tests.

For TDS both filters produced a similar reduction – the TDS dropped from 248ppm to 186ppm with the Brita filter water and to 167ppm with the Phox filter. The main difference between the Phox filter and the Brita filter was the pH. The Brita filter reduced the water from an initial pH of 7.4 to a reasonable 5.9 – where as the Phox filter reduced the pH all the way to 3.5. This, in my opinion is far too acidic. You can taste that this water is acidic and tell the difference between Brita, Phox and tap water in a blind taste test. For coffee the SCA recommands a pH of 6.5 – 7.5, so mixing tap water with the Phox water misses this range where as the Brita filter is within this range after mixing with tap water.

The water quality from the Phox filter means that I’ll be using the Brita filters from now on. Whatever the environmental benefits, I think they are outweighed by the water not being as nice.