Revisiting Hamilton’s Tap Water (For Accuracy)

Recently I have been playing with mineralizing distilled water to different GH:KH ratios to see how it affects coffee flavour using the ideal brew water chart from Water for Coffee as a guide and one of Matt Perger’s water recipes (found in the comments here) as a starting point. While doing so, I came across more up-to-date information that makes it necessary to re-examine my two previous posts. The purpose of this post is to explain the changes and then perform this quick re-examination.

My experimentation led me to a lot of math, learning about moles, dilution calculations, and summarizing things in equations. After all of this I couldn’t seem to reconcile Perger’s water recipe with the ideal brew water chart, although this recipe typically produces pleasant coffee. Perger said this recipe should lead to 100 ppm Mg and 50 ppm KH. Whichever way I did the math it added up to 24.5 ppm Mg and 62.1 ppm KH.

Since I was confident in my math at this point, I concluded that maybe Perger wasn’t trying to hit the ideal realm of the brew chart, or that he mistakenly based his math on the chart as though it were presented in ppm with [ion] as [CaCO3], and it tasted good anyway. It turns out that the second conclusion was closer to the truth. But it wasn’t Perger’s mistake.

After a bit of research and reading through coffee’s deep web, I decided to go right to the source and ended up having a short Twitter exchange with Chris Hendon. As it turns out, the ideal brew water chart presented in WFC is presented in ppm with [ion] as [CaCO3] as opposed to [ion] as [ion], despite the book’s advocacy for the use of [ion] as [ion]¹ as the standard for ppm measurement.

This means that my previous two blog posts about Hamilton’s water as it relates to coffee brewing must be re-examined. The data from those posts are correct, however the analysis of the data assumes that the brew chart is presented with ppm as [ion], which is not what we want if we are working with the ideal brew water chart from WFC.

Thus, let’s re-examine.

Testing Hamilton’s Tap Water (For Coffee)
Here is the data presented with [ion] as [CaCO3]:

Mar 17, 2016 – Mg: 65.6 ppm, Ca: 87.5 ppm, KH: 91-93.4 ppm
Mar 18, 2016 – Mg: 32.8-49.2 ppm, Ca: 87.5-92.5 ppm, KH: 93.4 ppm
Mar 19, 2016 – Mg: 65.6 ppm, Ca: 87.5 ppm, KH: 88.5 ppm
Mar 20, 2016 – Mg: 82 ppm, Ca: 93.8 ppm, KH: 91 ppm
Mar 21, 2016 – Mg: 65.6 ppm, Ca: 87.5 ppm, KH: 93.4 ppm
Mar 22, 2016 – Mg: 65.6 ppm, Ca: 81.3 ppm, KH: 93.4 ppm
Mar 23, 2016 – Mg: 82 ppm, Ca: 93.8 ppm, KH: 93.4-98.4 ppm

Average – Mg: 63.6 ppm, Ca: 88.9 ppm, KH: 92.9 ppm

Within this sample set our Mg content fluctuates notably, while Ca and HCO3 (KH) remain fairly constant. If we look at our average reading, we get a GH of 152.5 ppm and KH of 92.9 ppm. In this sample set, our GH varies +/- 30.9 ppm and our KH varies +/- 5 ppm.

In short, our GH will generally be within the ideal range of the ideal brew water chart and the KH will still be pretty far from ideal. Thus, Hamilton tap water may leave our coffee flat and chalky, which is the same conclusion as before. Ideally our water filtration would bring KH levels down to somewhere between 32.5 ppm and 75 ppm while leaving our GH levels (Mg and Ca) relatively the same.

Filtering Hamilton’s Tap Water (For Home Brewing)
The data with [ion] as [CaCO3]:

Tap water – Mg: 49.2 ppm, Ca: 81.3 ppm, KH: 91 ppm
Brita filtered tap water – Mg: 49.2 ppm, Ca: 68.8 ppm, KH: 32 ppm

The tap water in this second test is similar to some of the data from the first test. The tap water had a GH of 130.5 ppm and KH of 91 ppm. After Brita filtration the GH was 118 ppm and the KH was 32 ppm. These results actually put us right on the border of ideal and acceptable water in the ideal brew water chart.

If you brew coffee in Hamilton, the Brita filter should take your tap water from poor for brewing to acceptable or ideal for brewing, depending on the tap water that day.

¹The difference is discussed in the corrigendum to the book posted here on 10-10-15.


Filtering Hamilton’s Tap Water (For Home Brewing)

[Having discovered new information, the data from this post has been revisited here.]

Today I tested my home brewing water with my titration kit. I also tested my tap water again for comparison. I wanted to post the results online in case anyone finds them helpful.

My home brewing water is simply tap water filtered through a Brita pitcher filter. The filter is currently about a month or two old. (Ew. Gross. Yeah. Whatever.) The pitcher has been flashing the “change soon” light for a couple of days, but has not yet flashed the “change” light. (See? It’s fine.)

I used the Red Sea Pro Test titration kit. I followed the same procedure as I did here, except this time I rinsed my sample vials and sample syringe with tap water before measuring the tap water, and with Brita filtered water before measuring the Brita filtered water.

Yellow rubber gloves were worn, and titration ensued.

Here are my results:

Tap water – Mg: 8-12 ppm, Ca: 32.5 ppm, KH: 111 ppm
Brita filtered tap water – Mg: 12 ppm, Ca: 27.5 ppm, KH: 39 ppm

There are a few things I would like to point out.

Firstly, the tap water was quite consistent with the samples from my first experiment. This is good to see. Consistency = more frequently good coffee.

Secondly, the GH. GH stands for general hardness, the “G” coming from “general”, and the “H” coming from “hardness”. Brilliant. General hardness is our calcium and magnesium content combined, in ppm. According to today’s measurements, our GH is in the 39.5 ppm to 44.5 ppm range for both waters. It’s a bit low. We know from Water For Coffee that we want our GH to be 50ppm or higher for ideal extraction capabilities.

It also looks like the Brita filter may have lowered the calcium content just a little bit. I don’t want to make any major conclusions about this. However, the Brita website says that it does reduce the concentration of calcium and magnesium. And it may have put us just a bit further off from the 50 ppm GH minimum.

Thirdly, the KH – carbonate or temporary hardness. This one I am willing to give a little more weight to. This is more in line with other results I’ve had measuring Brita filtered tap water. It is also a pretty drastic shift. And it is a step in the right direction.

As I mentioned in my last post (I’m just going to keep linking you to that), we also know from Water For Coffee that too much carbonate hardness can leave coffee tasting flat and chalky. 111 ppm is probably going to be too much. At least according to Colonna-Dashwood and Hendon, the authors of the book. And they know their stuff.

Luckily, the Brita filter brings Hamilton water down to 39 ppm, a much more reasonable KH level. Reasonable, but not ideal. As consistent as it is, the water composition will vary slightly day-to-day. Today the KH happened to be at a point where it would be ideal – if the water had a higher GH, in the 50 ppm to ~65 ppm range. It’s about balance. Even if we had 50 ppm in GH, our KH might fluctuate a little bit tomorrow and put us off of ideal water composition. At these low levels of GH and KH there isn’t a lot of leeway.

However, the Brita filter does take Hamilton water from less-than-acceptable to acceptable. It’s progress. And my coffee is tasting pretty good at home. Actually, quite good, more often than not. I guess it can only get better.

I will keep experimenting with ways to have better brewing water at home. For now, the Brita filter is doing pretty well and is a definite step in the right direction for Hamilton home brewers looking to take their brew game to the next level.

I’d love to hear what people are using for their brewing water. Let me know in the comments below.

[Edit: The KH measurements in this post were originally posted in [ion] as [CaCO3]. However, since we are more interested in bicarbonate, I have converted those measurements to display ppm as HCO3.]