Rpavlis water in La Marzocco GS3

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
btalcox0715
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#1: Post by btalcox0715 »

Hi all,

Currently have a GS3 on the way and I'm trying to land on a suitable and sustainable water source to supply the machine. I have an email out to La Marzocco to see what their response is, but everything so far has been more/less pointing back to their water specifications PDF which outlines the general parameters of suitable water. They recommend TWW (half the prescribed packet per gallon, that is), but given how much coffee I make + the water waste of the MP, that'll be a costly option over time. I'm drawn to the Rpavlis water due to the sustainable and economical nature of it, but every time I read up on it, there is always some cases of people stating they had scale or it caused issues etc. etc. (which, I _am_ inclined to think something else is generally at play during those cases).

With that, does anyone have any guidance? Say I work the recipe out to something like 70mg/L (70 ppm) potassium bicarbonate--is this effectively acting as the "hardness" that La Marzocco recommends for their 70-100 ppm Total Hardness? From a CaCO3 equivalent hardness, it would be 0, though, right?

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homeburrero
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#2: Post by homeburrero »

Rpavlis is unusual compared to many recommendations because it does have zero hardness - no calcium or magnesium at all. In fact nothing that might cause scale deposits. It also has no minerals that might cause corrosion - no chloride, no sulfate. It just has bicarbonate, and about the right amount of that to buffer acidity and keep a healthy protective copper oxide layer on brass and copper.

There are some that believe you need some hardness minerals in the brew water for good taste, but that is debatable, and can be decided for yourself based tasting your coffee. One counterargument about the need for hardness minerals in the brew water comes from the fact that the water percolating through the puck is loaded with minerals that dissolve out of the ground coffee itself. A one ounce shot of espresso contains 20 - 30 mg of magnesium. Converted to conventional hardness measures that would be over 3000 mg/L as CaCO3! So having 100 mg/L or so in the incoming water doesn't seem like it should make a big difference.

There used to be a common argument that you needed some hardness minerals to lay down a layer of 'protective scale' but that's very debatable. Limescale deposits in an espresso machine are porous and unevenly deposited, so don't provide much protection. More importantly, if you are accumulating limescale deposits you will need to periodically descale, and descaling solutions are corrosive and can remove protective oxide layers.

There's some discussion, including a graph showing the La Marzocco hardness/alkalinity zone amidst other water recommendations in this thread: Recommended Water Total Hardness Range (La Marzocco water specs)
Pat
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btalcox0715 (original poster)
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#3: Post by btalcox0715 (original poster) replying to homeburrero »

Okay that's really helpful. I guess what I'm concerned about is anything "negative" towards the machine by using Rpavlis water. That shouldn't be the case right? And I guess at the end of the day, I can always add a small amount of magnesium sulfate to bring the hardness up a little bit

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homeburrero
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#4: Post by homeburrero »

btalcox0715 wrote:I guess what I'm concerned about is anything "negative" towards the machine by using Rpavlis water. That shouldn't be the case right?
That's my opinion, much of it based on posts by the late Dr Pavlis who I believe was very expert in this area.
btalcox0715 wrote:And I guess at the end of the day, I can always add a small amount of magnesium sulfate to bring the hardness up a little bit
Yes. You can do that without increasing your scale risk and also to see if it gives you a taste improvement. About 0.7 grams of Epsom (magnesium sulfate heptahydrate) per US gallon would give you a total hardness bump of 75 mg/l as CaCO3, bringing you into La Marzocco's recommendation range for hardness. It would also add 72 mg/L of sulfate ion. Sulfate is not as bad as chloride for corrosion risk, and you do have the bicarbonate protection there, but still may be prudent to try half that amount of the mag sulfate.
Pat
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