Mixing waters to achieve SCAE core zone values

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
Menn_o

#1: Post by Menn_o »

Hi All,

I recently took the plunge from a full automatic to a semi automatic. I started reading up on everything I can about espresso beans, preparation, machines, grinders and ended up in the rabbit hole called 'water'. So I read the SCAE water chart report, other Internet sources and many posts in this forum and I am now thinking about the best way to achieve good water for my machine. First to prevent scaling and second (of course) to achieve good taste.

I live in an area with relatively good tap water (Hardness of 7,5 dH and Alkalinity of 7,94 dH, almost 1:1 ratio) that is free of odeur or chlorine and tastes really good. Where I live it is not easy to obtain distilled water and salts to make my own water from scratch. So, I am now considering mixing waters. It can be quite easy and could give very consistent results. There are two mineral waters (Spa Reine and Saskia Loningen) I can easily obtain that are very low in GH and KH, which seem like a good basis. Then there are some other waters I want to use to mix it with to bring the alkalinity and hardness in the right range.




Now I have come up with the following mixtures to land in the SCAE core zone of 70-100 ppm hardness and 40-60 ppm alkalinity.
  • The tap water mixtures are easiest of course, but have a somewhat higher Sodium, Chloride, Sulphate and TDS levels compared to using Bar_le_Duc instead.
  • The Spa Jumbo mixture has the best value, but I don't know what the resulting pH would be as Spa has a quite low pH of 6
Would mixing water be a good approach and which mixture would you recommend?








Btw, an alternative would be using a water filter pitcher from Brita or BWT. But given the relatively 'soft' water, this would reduce hardness and alkalinity too much. Further, it only allows me to move along the GH:KH = 1:1 line which is below the SCAE core zone. And it reduces the pH of the water as well. By how much I don't know.

Thanks for reading!

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homeburrero
Team HB

#2: Post by homeburrero »

Nice post! You've clearly put a lot of research and thought into this. I assume that you plan to run your tap water through some sort of charcoal or carbon block to handle particulates, chlorine, off tastes and odors.

Re
Menn_o wrote:to land in the SCAE core zone of 70-100 ppm hardness and 40-60 ppm alkalinity.
That is a good interpretation of their chart, but I think you can easily go lower on the hardness. No problem in my opinion going even lower than that core zone on hardness because that bottom edge is based on fairly iffy opinions - - follows a line that Colonna-Dashwood and Hendon used in their Water for Coffee book. That was as reasonable a choice as any given that there is so little science or agreement about how much hardness, if any, you need for optimal taste. So I think you can go lower in hardness, especially if you want non-scaling water. A lot of people here on HB use a zero hardness 'rpavlis' water with no complaints.

The tolerance for chloride depends on a complex corrosion risk decision. In your waters where you have 50-55 ppm as CaCO3 alkalinity I think you're probably OK with those 20 - 40 ppm chloride ion numbers. But for a valuable or especially a vintage machine you may want to go lower on the chloride values. Note that La Marzocco recommends that chloride be below 30 ppm and Synesso recommends that it be below 15 ppm for corrosion risk reasons.


Menn_o wrote:The Spa Jumbo mixture has the best value, but I don't know what the resulting pH would be as Spa has a quite low pH of 6
That Spa water pH is probably due to a higher than normal CO2/carbonic acid in the water. After exposure to air the CO2 would gas off and the pH would come up. In any of your mixes with 50+ ppm alkalinity I think you can expect an above neutral pH after the water is open to the atmosphere.
Menn_o wrote:Btw, an alternative would be using a water filter pitcher from Brita or BWT. But given the relatively 'soft' water, this would reduce hardness and alkalinity too much.
Yes, I think it's prudent here to avoid any filter that has a WAC decarbonizing resin. Your tap has that high chloride, which argues against decarbonizing. (decarbonizing, aka WAC resins capture hardness ions (Mg++ and Ca++) and release an equivalent amount of H+ ions, which reduce alkalinity and pH of the water, which would increase corrosion risk from that chloride.) You do need to take care of chlorine (which is different than chloride) in the tap water, which can be handled by simple carbon/charcoal filtration.

But I think you could consider a ZeroWater filter, which does remove chloride (along with everything). If you mix 35% charcoal filtered tap with 65% Zerowater you would have:
total hardness: 47 ppm as CaCO3
calcium ion: 14 ppm => 35 ppm as CaCO3
alkalinity: 50 ppm as CaCO3
chloride ion: 18 ppm

Which is a reasonably non-scaling water with good alkalinity and not too bad chloride. The downside there would be the cost of Zerowater filters given your 350 ppm TDS tapwater. Each 18 € filter would only treat about 40 liters, so your filter cost for the 35% mix could be up in the .8 €/L ballpark.

P.S.
The core zone chart you pictured in your post is from their SCAE water chart, and is not quite what they intended - got shifted up in the image before going to press. Discussed here: SCAE Water Chart is available online . You can find a good representation of their core zone aligned properly Per Marco Wellinger's explanation in my old post here: Good references on water treatment for coffee/espresso
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

Menn_o (original poster)

#3: Post by Menn_o (original poster) »

homeburrero wrote:Nice post! You've clearly put a lot of research and thought into this. I assume that you plan to run your tap water through some sort of charcoal or carbon block to handle particulates, chlorine, off tastes and odors.
Thanks for the detailed response. Our drinking water does not contain chlorine, particulates or odors. It is very clean and high quality. Even zerowater praises it. https://www.zerowater.eu/is-bottled-wat ... tap-water/


homeburrero wrote: Re That is a good interpretation of their chart, but I think you can easily go lower on the hardness. No problem in my opinion going even lower than that core zone on hardness because that bottom edge is based on fairly iffy opinions - - follows a line that Colonna-Dashwood and Hendon used in their Water for Coffee book. That was as reasonable a choice as any given that there is so little science or agreement about how much hardness, if any, you need for optimal taste. So I think you can go lower in hardness, especially if you want non-scaling water. A lot of people here on HB use a zero hardness 'rpavlis' water with no complaints.

The tolerance for chloride depends on a complex corrosion risk decision. In your waters where you have 50-55 ppm as CaCO3 alkalinity I think you're probably OK with those 20 - 40 ppm chloride ion numbers. But for a valuable or especially a vintage machine you may want to go lower on the chloride values. Note that La Marzocco recommends that chloride be below 30 ppm and Synesso recommends that it be below 15 ppm for corrosion risk reasons.
I based the hardness range of 70-100 also on recommendations from La Marzocco https://techcenter.lamarzocco.com/jsp/T ... ulator.jsp. So I guess it would be good to have a better understanding of what hardness is the best range, both for the machine as well as for taste. My preference is dark and full bodied espressos.


homeburrero wrote: That Spa water pH is probably due to a higher than normal CO2/carbonic acid in the water. After exposure to air the CO2 would gas off and the pH would come up. In any of your mixes with 50+ ppm alkalinity I think you can expect an above neutral pH after the water is open to the atmosphere.
So you recommend to let the water breathe for an hour (?) before filling up the watertank in the machine?


homeburrero wrote: But I think you could consider a ZeroWater filter, which does remove chloride (along with everything). If you mix 35% charcoal filtered tap with 65% Zerowater you would have:
total hardness: 47 ppm as CaCO3
calcium ion: 14 ppm => 35 ppm as CaCO3
alkalinity: 50 ppm as CaCO3
chloride ion: 18 ppm

Which is a reasonably non-scaling water with good alkalinity and not too bad chloride. The downside there would be the cost of Zerowater filters given your 350 ppm TDS tapwater. Each 18 € filter would only treat about 40 liters, so your filter cost for the 35% mix could be up in the .8 €/L ballpark.
Thanks for the reference for Zerowater. I didn't know them, but did some reading and there EU office is located in The Netherlands where I live. It looks like a good product. I could of course mix Spa with tap-water in a 75%/25% ratio, to get similar results. But a filter may give more flexibility to achieve certain ratios, while bottled water only comes in a liter or 1.5 liter, so you are more or less bound to ratio increases of 25% when trying to refill the 2L watertank of a machine. Further, the TDS of 350 for tap water was a rough guess from my side based on the conductivity of 500 uS/cm. So it could be less in practise.

Menn_o (original poster)

#4: Post by Menn_o (original poster) »

By the way, the updated chart discussed here seems really off. Water for Coffee v2





The lowest alkalinity here in the ideal brewing zone is 20 ppm CaCO3. I have never seen such a low value, expcept for filter coffee maybe. But it almost seems as if the axis got mixed up by all the ratios applied.

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homeburrero
Team HB

#5: Post by homeburrero »

Menn_o wrote:Our drinking water does not contain chlorine, particulates or odors.
Very interesting, thanks! -- I learned something new here. I found an article online about how Dutch water utilities get by without the chlorine or chloramine disinfectants that almost everyone else relies on: The Dutch secret: how to provide safe drinking water without chlorine in the Netherlands.

Menn_o wrote:By the way, the updated chart discussed here seems really off. Water for Coffee v2
It is divergent from most recommendations. It may be OK for brewed coffees, but the alkalinity is lower than typically recommended for espresso machine health. And the upper (right side) border for alkalinity can be much higher for espresso than for brewed coffee. Espresso tolerates a nearly 10x higher alkalinity than brewed coffee before the taste is noticeably dulled due to buffering of coffee's acidity by the brewing water. Finally, I think the lower border lines for hardness in all of these 'ideal zones' are not to be taken too seriously. (As I mentioned earlier, the very popular rpavlis recipe has zero hardness.)

P.S. [edit addition]
Menn_o wrote:So you recommend to let the water breathe for an hour (?) before filling up the watertank in the machine?
By the time you pour and mix the two waters together in a mix that has 40+ ppm alkalinity, it should be fine for use in an espresso machine. As the water is heated in the boiler more CO2 will boil off. If your alkalinity is good I think you don't need to worry about the pH of your brew water.
Pat
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Menn_o (original poster)

#6: Post by Menn_o (original poster) »

So I thought 'before I go ahead with mixing water, let's test the hardness and alkalinity'. So I have the testkit from Brita and 2 testkits from aquarium brands. They are all drip tests that will give a change in color when the value is reached. They are not that precise, but I wanted to see what they give. Well, the results are wildly off.:
Brita testkit: GH = 10, KH = 8
Colombo testkit: GH = 8, KH = 10 (no, I did not mix it up. I triple checked)
Salifert testkit: KH = 8.9 (most precise method).

So this is totally unhelpful and these testkits are very inaccurate. I will now test them against some mineral waters. See if any of the test kits will give the same results as what the water says on the label (which is probably also just some average). It is too bad there is no good way to calibrate the whole thing. Are there more reliable home test kits for this?

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homeburrero
Team HB

#7: Post by homeburrero »

Drop count test kits like these can easily be off by a degree or even two. You can often get better precision by stretching them, especially for softer waters. Stretching simply means using a larger water sample and the same titrant, and adjusting accordingly. For the popular API kits, which instruct you to use a 5 ml sample, you can instead use a 10 ml sample, then adjust the table so that each drop corresponds to a half degree (8.9 ppm as CaCO3) rather than a full degree (17.9 ppm as CaCO3).

That Salifert kit looks pretty nice, and allows you to use a graduated syringe to measure the titrant volume instead of just counting the drops. At your level I see no reason to stretch it. You aren't doing quantitative chemistry here and your value of 8.9 °dKH, which would be maybe ± 0.3 °dKH is more than precise enough.
Are there more reliable home test kits for this?
Salifert and Red Sea don't have GH kits* but you can measure Ca and Mg and add the two at very low precision. My favorite GH kits are from Hach.

P.S.
Another nice thing about Salifert is that they correctly describe the kit as a KH/Alkalinity kit. Unlike the Brita test kit that calls their KH kit a "temporary hardness" kit, which contributes to confusion about how hardness is quantified.


All drop titration kits for KH, "carbonate hardness", or "temporary hardness" are actually simple alkalinity tests that measure the acid buffering capacity of the water. For most, but not all natural waters, the alkalinity is the same as the carbonate hardness and temporary hardness. But in any water that has been softened, or made from a recipe where the alkalinity exceeds the total hardness, your carbonate (or "temporary") hardness is equal to the total hardness and not the alkalinity.

*[Edit addition] I see that Salifert does gave a freshwater GH drop titration kit. It's not the Pro version and does not have the syringe nor the separate indicator, just uses a titrant+indicator like the API kits and drop counts. You could probably use the syringe from your alkalinity kit.
Pat
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Menn_o (original poster)

#8: Post by Menn_o (original poster) »

Thanks. I also tested the mineral waters and the results are all over the place. Both Brita and Colombo seem to overestimate GH and KH. I did what you recommended to use 10 ml samples, I figured that myself already, also for tapwater.
The Saskia water is measured at GH 7 and 6 dH for Brita and Colombo, whereas it should be 4,8. KH comes in at 2 for all 3 tests, which is a bit too high, but the alkalinity is so low, it is hard to measure. At least the test didn't come up with very high values.
For Spa, Brita measures GH 3, whereas Colombo puts it right at 1. The Spa water may be too soft though for proper measurement.

When I measure Bar le Duc the results are very similar to what I measured with tap water (which in principle is what it should be). So:
Salifert measures KH at 8,9 - same as Tap water - but it should be around 7,5. So also here it seems to give too high values. I repeated the test multiple times and it keeps giving me this value. So who or what is right here?

Then, also for Bar le Duc
Brita measures KH = 9-10 and GH = 10
Colombo measures KH = 11 and GH = 10.
Both too high compared what the producer states on the label as well, but again, who knows who's right?

Maybe you are right that when Alkalinity is same or higher than Total Hardness, these kits don't work well.

As for the right water mixtures I think it is simply best to rely on the values that the producers give and use Spa or ZeroWater in the mix as they can be safely assumed to have very low GH and KH. A mix of those with tap water puts me a little below the ideal zones, but you mentioned this is no problem. I could experiment with exchanging some of the Spa/Zerowater with Saskia water to gently increase the hardness if I want to.