Hi there,

I'm soon upgrading from a heat exchanger (HX) to a direct-plumb dual boiler which has implications on my water "management". With the HX, I mixed distilled water with tap water to create a well-balanced composition - both "safe" (in terms of corrosion/scale) and simultaneously "tasty" for my espresso.

As my new machine will be plumbed-in, I'm looking more closely at the composition of my tap water:

- TDS: 218
- pH: 7.3
- General Hardness (GH): 8 dh (114 ppm CaCO3)
- Carbonate Hardness (KH): 6 dh (85.8 ppm CaCO3)
- Temperature (Measured): 71 degs. (F)

If you plug these all into a Langelier Index (LI) calculator (like Barista Hustle's @ https://www.baristahustle.com/app-archi ... alculator/, you'll find that:

- At room temperature: -0.5 (Slightly corrosive but non scale-forming)
- At brew boiler temperature (203 F): 0.8 (Slightly scale forming and corrosive)
- At steam boiler temperature (257 F): 1.2 (Scale forming - treatment required)

So, not too shabby for tap water. If anything, I'd say I should install a water softener in the water line, which might bring the values to -0.8. 0.5, 0.9 respectively. My biggest concern is the ("slightly corrosive") water sitting in the boilers at room temperature when not in use.

With that in mind, what would you do in this situation? Do people drain their boilers "overnight" (or when not in use)? Or should I just install a water filtration system like Bestmax? I don't see how else to get around the "slightly corrosive" room temperature water. Or maybe if I keep the machine on for half of the day, and off for the other half, then the "slightly corrosive" and the "scale forming" will cancel each other out

Thanks!

The idea that negative LSI water is corrosive is a gross oversimplification. It's based on the idea that you need some 'protective scale' in a plumbing system. Corrosion is more complex than that, and the idea of protective limescale is debatable, especially in espresso machines. The late R. Pavlis (chemistry professor and HB member rpavlis) argued that limescale is porous and not that protective, and that it doesn't deposit as a uniform protective layer in espresso machines, and most importantly that if you are depositing limecale you will need to periodically descale the machine, and descaling can strip the truly protective oxide layer from brass and copper and expose metals to corrosive acids.

Many of the popular 'scale free' waters and recipes used in espresso equipment are either very negative LSI or are not even suitable for doing an LSI calculation.

bear wrote:My biggest concern is the ("slightly corrosive") water sitting in the boilers at room temperature when not in use.

I see no reason for concern here. It may be that overnight the room temp boilers are dissolving a smidgen of the previous day's deposited limescale, but it would precipitate back out when the boilers heat up the next morning. Normally you just do your LSI calculation based on the boiler temps when the machine is at full temp and base your scale deposition estimate on the water throughput. See Jim Schulman's Insanely Long Water FAQ for info.

To decide if your water may actually be corrosive you need to look primarily at the alkalinity (conventional guidance is to assure that it's 40 mg/L CaCO3 equivalent or higher) and especially the chloride ion. Chloride ion (which is not the same as chlorine) can be very corrosive, especially to brass and copper but also to stainless steel.
See Boiler-safe level of chlorides (and other compounds) in water.
and Chloride in Water - Recommended Acceptable Ranges



High levels of sulfate might also be a corrosion concern. And frequent descaling, especially when not necessary, would be another corrosion risk.

P.S.
I should mention that the proper interpretation of an LSI index is very simple -- when LSI is less than zero the water should tend to dissolve limescale (calcium carbonate, CaCO3) and when greater than zero it should tend to deposit limescale.

bear wrote:Or should I just install a water filtration system like Bestmax?

Your water would benefit by some softening, and if you wanted to never have to descale the machine you would certainly need to soften it. There are three different ways of softening water:
1. a WAC resin decarbonizing filter like the BWT bestmax, which exchanges hydrogen for hardness cations (Ca and Mg). It tends to reduce alkalinity and acidify the water. These systems often use adjustable bypass heads that let you dial in the amount of softened water.
2. a SAC resin conventional softener that exchanges sodium or potassium ions for hardness cations. These are chemically similar to the familiar whole house water softener. They reduce hardness but keep all the alkalinity, and normally don't have an adjustable bypass head.
3. a reverse osmosis (RO) system. It removes most of most of everything, including the hardness, alkalinity, and other ions like chloride. For coffee equipment you need to add minerals back in using a remineralization cartridge or perhaps a blending valve.

#3 is often recommended if you have 15 - 50 mg/L or more chloride in your water.

For water that has low alkalinity or borderline chloride #2 is recommended over #1.

In your case if you know you have little or no chloride in the water you could use #1 and dial it in so that you end up with around 40 mg/L alkalinity, which you can test with a simple drop titration KH or alkalinity test kit.

This is great information, thanks homeburrero.

Is it enough to look at the chloride values in my city's published water report? Or might it vary too greatly by household? Based on the city's report, the chloride value (measured monthly) typically averages between 18-20.

Here's our 2020 and 2021 Inorganics Analyses:
https://www.fairfaxwater.org/sites/def ... s_2020.pdf
https://www.fairfaxwater.org/sites/def ... 0Water.pdf

bear wrote:Is it enough to look at the chloride values in my city's published water report? Or might it vary too greatly by household? Based on the city's report, the chloride value (measured monthly) typically averages between 18-20.

You're fortunate that your utility provides such an excellent water report. It clearly indicates a fairly constant chloride concentration. The 15 - 29 mg/L choride ion is high enough that the most conservative advice (from Synesso) might suggest using RO, but I think you would do fine keep it really simple and just use an Oscar/Bilt/Rocket pouch filter (a conventional SAC resin softener) in the reservoir to reduce the hardness and keep the alkalinity up. if you replace it every 6 months or so, and refill the reservoir when you shut the machine down for the night it should take care of any limescale issues. (Your water report verifies that the water is variable in hardness and alkalinity, but even at its worst it is not highly scale prone.) To take care of the chlorine, taste, and odor I would use a Brita 'Longlast' pitcher filter. The Longlast is nice because it does not reduce alkalinity nor acidify the water, which is important when you have borderline chloride.

Edit addition: I realized after posting that you're wanting a plumb-in and not a reservoir solution. So for you I think a GAC filter or a carbon block filter along with a conventional softener would do the trick. The Homeland filter from Clive Coffee is one example. Another that uses two filters in generic 10" housings is the filtration + softener setup from WLL or from Chris Coffee Service.

Thanks again - I appreciate all of your time spent helping me to understand what very quickly becomes a complex subject.

I've gone ahead and purchased the system from Clive - thankfully I have clearance underneath the sink for 18-20"!