Water from the hot water tap on an espresso machine

The other day I decided to try filtered water versus non-filtered water for pour over coffee and the result was that the filtered water was better.  This is not shocking since that was what I also concluded drinking the water straight, but since even our tap water is fairly soft and since coffee adds in a very strong flavor of its own it is not necessarily obvious that this would be the result.  I could have just as easily believed that the subtle differences would be masked.

http://www.roaste.com/CoffeeBlogs/wakeknot/More-experiments-water

Today I decided to try the filtered water versus the water in my machine’s boiler (which is filtered before going into the machine) pulled out using the hot water tap.  For these in the straight up water test I could tell a minor difference, but it was really, really subtle with the straight water winning by a nose.  With such a subtle difference it was even less obvious if there would be a favorite in the brewed coffee contest.  


I again used the same coffee as last time – Deep Cello Bossa and made two identical cups using the Timolino drippers each at the same temp and dose.  I confess I should have done this blind because I had a bias that I thought the non boiler water would be slightly better, but I had a bias the other way, too, as I would far rather be able to use the hot water tap than have to always heat up water every time I want to do pour over.


I made two cups and both were good and the truth is that I could not tell a real difference and certainly no difference that made one preferable.  Just in case bias was forcing me to decide this, since this was the best possible result for me I had my wife try them both.  This obviously is not a double blind test since I knew the difference and stats classes say double blind is much better than just blind, but I wasn’t sending the results onto the FDA so I figured I was probably okay.


After trying both she declared that she did not see a difference.  I thought that was pretty cool because I did not explain to her in advance that I was just testing water and she hadn’t known about my previous water tests, so I think she was under the assumption that I had given her two different coffees and not just different water so deciding they tasted the same was not one of the expected possible outcomes.


So my conclusion is that there may be a difference, but it is too subtle for us to tell and so I can get away with using the hot water tap.  The far bigger differences will be things like the coffee, the dose, and even the distribution.  I think these results might be very different though for someone with much harder water.