Fear of Water

November 28th, 2010

I was going to do revisit an old post about why someone’s coffee might taste bad, talking about the amount of dull burrs out there, as well as a bit more on cleaning and other stuff. However, one aspect alone deserved a post on its own. I will say right now that this is particularly relevant to water in London. It isn’t your friend.

If you live in London and want to know what you are up against then put your postcode in here. The news isn’t good. According to the website the water at the roastery is pretty bad. 284.7mg/l calcium carbonate. That is a lot, and our own testing confirms this at around 290mg/l and our Total Dissolved Solids (TDS) are up around 450-480mg/l. To give that some context this is a rough breakdown on hardness (from wikipedia – definitions may vary):

Soft: 0-60 mg/L
Moderately hard: 61-120 mg/L
Hard: 121-180 mg/L
Very hard: 181 mg/L

On this kind of scale this makes London water ridiculously evil! Compare it also to the SCAA published water recommendations that are found in this pdf.

Coffee Equipment

Water this hard is going to take your coffee machine down. It is going to cause failure incredibly quickly if it isn’t treated. Probes are going to get covered in scale, boilers will overfill, flow restrictors will clog up, heating elements will start to become less and less efficient, valves will start to have issues – the list goes on. It will be expensive to fix, regardless of whether you include lost sales in the financial damage.

I’d say 9 out of 10 machines issues (across all manufacturers) that I’ve seen in London in the last three years have been down to water. Which means that 9 out of 10 are preventable. If you are running commercial coffee equipment of any kind and not paying attention to your water treatment then there is expensive trouble ahead.

Single boiler/HX machines tend to suffer through bad water better than dual boilers. They can have their flow restrictors on the cold water side, which means that they are much less likely to scale up than flow restrictors inside/on the groups of brew boilers. However, there are still lots of parts that will suffer and impact overall performance.

The challenge with scale is that it is often out of sight (and out of mind), and therefore – if you aren’t paying attention to your water – then the only time you encounter it is when it reaches critical mass and something breaks. For those interested our water is at the roastery is approximately 68mg/l, with a TDS of around 140mg/l but we’re using an RO system.

If you own coffee equipment in a hard water area then you should be keeping an eye on your water. Test kits are cheap and easy to use. This isn’t the place to discuss how you ought to be treating water, as there are a variety of solutions for different needs. No excuse not to test though!

Brewing and hard water

Coffee brewed with very hard water isn’t very delicious. As a really simple exercise brew two press pots, one with very hard water and one with soft water with a TDS of around 150mg/l. Same grind, same brew temp, same steep time. The results are quite interesting. Hard water produces a chalkier, slightly heavier cup, that is completely and utterly boring. Soft water produces a far more delicious, complex and interesting cup with much better acidity. The difference is shocking to people, especially those who expect it to be subtle. These kind of issues aren’t limited to infusion brewing – espresso suffers as well. I should probably note that TDS is a massive factor here – very soft water with a high TDS isn’t going to make you great coffee.

So if your brew water at home is hard then there is good news and bad news:

Bad news: You really aren’t getting anything near the best out of the coffee you buy
Good news: If you’re already enjoying it then it could easily get ten times better just by using better water!

I haven’t delved very deep into water chemistry here – if you want something hardcore then perhaps check out Jim Schulman’s insanely long Water FAQ. This wasn’t really a long post about water chemistry and its effect on coffee, more a reminder to keep an eye on water quality as it has a massive impact on all aspects of brewing. A long post on water quality may be something for the future – if only as an incentive for me to understand it all better than I do now! If people want to add any corrections or clarifications to the above then that would be very welcome. I can’t help feeling a little worried that I’ve oversimplified here…

When it comes to home brewing then the choices are either to soften your water or purchase bottles of something suitable – which does feel a bit weird to recommend. I really must do a bunch of testing on Brita filters to find out what they are doing, and how well they are doing it! If anyone has any good info I’d be very interested to see it.

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