Sideshow wrote:Thanks. Is this all you folks really do? Just throw some potassium bicarb in some distilled water?

It seems too good to be true.

Yes and it works fine on my speedster so no worries.

About 8 years ago I had my first conversation here with rpavlis, where he convinced me of the benefits of using distilled water with enough KHCO3 added to it to make the solution non-corrosive.

I used it for 5 years in my LP Romantica Pro, and for the past 3 in my LIvia 90, and have not descaled either since. Opening the top of the LP or disassembling the group disclosed what appeared to be a new machine. Group rebuild frequency seemed to be reduced by more than half.

I made the Livia from a couple of non-working machines and I went through it thoroughly when disassembled. I have not opened it since and have had no issues. Since what the potassium bicarbonate does is to make a buffer solution, keeping pH approximately the same regardless of concentration, I don't have a routine for addition, the Livia will tell me if I don't have enough ions in my distilled (it won't run).

This week someone posted about how this water solution seemed to really improve their shot quality.

The scale buildup solution is just a matter of chemistry, so I'm not surprised that the solution works to prevent it. I'd like to know more about taste experience upon changing to the Rpavlis solution. I'm going to try it myself this week since, why not? So, what has everyone taste experience been?

I think it's great. It's all I use.
I dissolve 19 grams of potassium bicarbonate in 250 ml of H2O. Then with this solution I prepare 5ml ice cubes. When I have to prepare a gallon of solution for the machine I just drop one ice cube in the water. The final solution typically gives me 55-65 TDS.
For H20 I use a Zerowater pitcher (which gives me 0 TDS).

And your reward from using scale-free, chloride-free water? A machine with a key scaling point that looks like this after five plus years:
This is what to expect from good water

-Peter

Moka 1 Cup wrote:I dissolve 19 grams of potassium bicarbonate in 250 ml of H2O. Then with this solution I prepare 5ml ice cubes. When I have to prepare a gallon of solution for the machine I just drop one ice cube in the water. The final solution typically gives me 55-65 TDS.
For H20 I use a Zerowater pitcher (which gives me 0 TDS).

That's one good way of making the full strength R Pavlis water, which is 100 mg/L of potassium bicarbonate.

Forgive me but I can't resist adding a little chemistry discussion that might be interesting or useful to know ...

Note that the actual total dissolved solids here is clearly 100 ppm (because it has 100 mg of mineral dissolved in a liter). But it's nevertheless true that it would read about 60 ppm on a typical inexpensive TDS meter (NaCl calibrated with factor of 0.5). The difference is just due to TDS meters measuring conductivity as a rough estimate of dissolved solids, and different minerals can have very different conductivities. A TDS meter calibrated to a 4-4-2 solution with a calibration factor of 0.65 would read about 80 ppm on this water.

The alkalinity of this 100 mg/L recipe is 50 mg/L as CaCO3 - nicely in agreement with old and new recommendations in SCAA and SCA publications.
(CaCO3 and KHCO3 have about the same molar mass - 100g/mol, but each CaCO3 molecule neutralizes two H⁺ ions, and each KHCO3 molecule neutralizes only one.)

And regarding pH. As hankbates says, the HCO3 is a buffer which acts to neutralize acids in the pH range we use for coffee water. Without it a little acid can cause a large drop in pH. The amount of bicarb that you add does have some effect on pH of the mix (assuming pure distilled with nothing but potassium bicarb here):

Alk □ pH □ pHeq □ mg/L KHCO3
10 □ 7.5 □ 6.0 □ 20
20 □ 7.8 □ 6.4 □ 40
30 □ 8.0 □ 6.7 □ 60
40 □ 8.1 □ 6.9 □ 80
50 □ 8.2 □ 7.0 □ 100
60 □ 8.3 □ 7.1 □ 120
70 □ 8.4 □ 7.2 □ 140
80 □ 8.4 □ 7.3 □ 160
90 □ 8.5 □ 7.4 □ 180

In the above, the pH is the expected pH (from http://www.aqion.onl/show_ph ) at 25℃ in an open container at equilibrium with atmospheric CO2. The pHeq is the Puckorius pHeq, which might be argued as best for steam boiler scale/corrosivity estimation. (In natural waters you might use pHeq as the appropriate pH for LSI calculations, but in water like this that has no calcium whatsoever, doing an LSI calculation would not make much sense.)

Ok, going to finally give this a try. I've been using Crystal Geyser from Mt. Shasta up till now.

I just went ahead and got a pound of potassium bicarb and a milligram scale. I'm just going to throw 100 mg in a liter of distilled water and be done with it.

I wonder if, over time, this water will eat away at the scale that's already built up in my machine?