Longtime reader here, first time poster. After a lovely decade with a Gaggia Classic, upgraditis finally got the best of me and I made the leap to a fancy HX machine. Life is good, except the newfound paranoia about water quality... and hence this post.

Leading up to the HX purchase, I spent countless hours reading the water quality FAQs and Favorites, and generally felt pretty confident about my water quality. Our utility provides real-time updates based on the treatment plant tests, and the annual report gives the following ranges observed throughout the year:

Alkalinity, Total as CaCO3 (ppm) 21-53
Calcium (ppm) 4-15
Hardness as CaCO3 (ppm) 16-54
Magnesium (ppm) 1-4
pH (pH) 9.0 - 9.4
Potassium (ppm) <1-1
Silica (ppm) 7-10
Sodium (ppm) 5-16
Total dissolved solids (ppm) 33-110

I used some test strips at home to double check that the total hardness and alkalinity (as CaC03) agree with what I see at my tap, and they seem to (at least, at the resolution of the test strips). A disagreement is that I measure a more neutral pH of ~7.2 at my tap; I am not sure what the reason is for the discrepancy with the measured values at the treatment plant.

The total hardness and alkalinity numbers seem to put me in the green zone of this convenient and informative chart, which made me feel pretty confident. Also worth noting, I only descaled my Gaggia about once every 2 years as a prophylactic measure, and never had any scale issues. When I did a teardown last year to replace all seals, etc. I did find some scale deposits on the aluminum boiler (which I understand to be more susceptible to scale than stainless steel), but the copper tube and plated brass group head (forming the bottom of the boiler) were all scale-free.

Anyway, now that the HX machine has arrived, the espresso is great but water quality paranoia has got the best of me since the new HX machine is a much more sophisticated beast than the Gaggia Classic. I'm hoping the community experts can provide some guidance as to whether supplemental treatment is needed to maximize the lifespan of my machine. I'm not opposed to doing something like 70/30, but current water tastes great in the cup (to me), so am wondering if it is necessary/recommended. My current understanding is that 70/30 (or similar) would definitely put my mind at ease since it eliminates calcium hardness altogether (so, no scale, ever), but maybe my hardness numbers are such that scale won't be an issue with an infrequent, albeit regular, descaling routine as part of preventative maintenance.

Thanks in advance!

Looks a lot like San Francisco water, where people typically just use a good carbon filter to handle the chlorine/chloramine. Your 4-15 mg/L calcium ion number indicates a calcium hardness (as CaCO3) of less than 38 mg/L so you should be free of limescale. Alkalinity looks good as it is, so you probably don't want to reduce that by using a WAC filter (or a jug filter like Brita that contains a little WAC resin.) If you have a filter on your refrigerator that should work.


You don't show your chloride number, which is key when being cautious about potential corrosion. Opinions about what constitutes too-high chloride vary, with Synesso recommending it be below 15 mg/L and La Marzocco recommending it be below 30 mg/L. San Francisco water should be below those levels.

Your pH disagreement is no cause for worry. They treat water to raise the pH and mitigate corrosion in the plumbing, and once it comes out and is exposed to air the dissolved CO2 in the water increases along with the carbonic acid, dropping the pH. For estimating scale and corrosion pay more attention to the alkalinity.

Thank you -- very helpful and reassuring to hear from an expert! FWIW, chloride levels are 4-8 ppm as reported by the utility, so they seem to be no cause for concern.

Because I like to fiddle, I decided to start experimenting with the rpavlis water recipe, using sodium bicarbonate instead of the usually recommended potassium bicarbonate. The sodium bicarbonate recipe can be readily inferred from all the other information on this forum. It is not directly relevant to my original post, but I am summarizing what I learned below for easy searching/reference/comment by other readers.

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rpavlis water recipe (sodium bicarbonate variation)

Concentrate recipe: Add 16.1g sodium bicarbonate to 750ml distilled water.

Water preparation: Add 1 Tbsp of concentrate to 1 gal of distilled water.
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Notes:
- The original rpavlis recipe uses 19.2g potassium bicarbonate instead of 16.1g sodium bicarbonate. Both result in the same equivalent alkalinity of 50mg/l as CaC03, and the conversion follows from molar masses as noted, for example, in this discussion.
- Prof. Pavlis noted either potassium bicarbonate or sodium bicarbonate could be used, but suggested he preferred the former because potassium is abundant in coffee beans, while sodium is not. I personally do not detect any off-putting sodium notes; individual tastes may vary.
- A low-alkalinity solution can be prepared using 1/2 Tbsp of concentrate to 1 gal of distilled water; possibly advisable for dark roasts.
- The concentrate can also be used as the buffer for 70/30 water. Add 6.3ml (a smidge over 3/4 Tbsp) to 1gal distilled water to get the desired alkalinity of 42mg/l as CaC03.