I’ve now had a chance to obtain and use the API GH & KH test kit. My remineralised RO water comes out as: GH 71.6 ppm & KH 53.7 ppm.

Does that sound appropriate for use in my espresso machine?

Thanks.

    mathof2 it’s slightly scaling at brew boiler temps and will scale more at service boiler temps so you’ll want to descale. If you’re using s skuma remineralisation bottle you might want to consider chloride and or sulphate content too.

        I’ve been using pure Skuma RO water in my Minima since I received it at the end of January. I drained the service boiler before refilling with the RO water. I thought I’d check the TDS reader I got with my Zero jug when I drained the boiler. When the water had cooled it was 432.

        I did the same test today after draining the service boiler from the pure RO Skuma water. It was 84.

        I know this isn’t the perfect test for analysing scale in the boiler etc. but using RO water seems a vast improvement on remineralused Zero water

          dutchy101 but using RO water seems a vast improvement on remineralused Zero water

          What were you remineralising the water with before the Skuma? And what’s the TDS from the pure RO water from the Skuma?

              Rob1 Thanks for your reply. I’m using a 2014 Londinium L1, so only one boiler. I don’t whether that matters compared to a dual boiler machine.

              The Skuma pre-prepared Coffee Balance infusion mixture is advertised as containing 20ppm Mg2+^ as CaCO3 and 10.8ppm HCO3 as CaCO3

              I wouldn’t know how to add chloride or sulphate to that, or in what quantities.

              • Rob1 replied to this.

                  mathof2

                  Not really, easier to descale but that’s about it.

                  Skuma used to advertise the Magnesium as coming from salt lake in Utah as Magnesium Sulphate so you could figure out how much sulphate there is. Looks like they’ve dropped the calcium chlorid for the coffee formulation. Out of curiosity what is the Skuma outputting without the remineralisation?

                    TDS reading wirh the Pure RO water from my Skuma tends to be about 60. My tap water is generally about 350 - 400.

                    I haven’t done a GH or KH test on the pure RO water - need to do it at some point.

                    MediumRoastSteam I used to remineralise the Zerowater with sodium bicarbonate. I’d make up 5l of Zerowater and add 320mg of sodium bicarbonate to 5l

                    • LMSC replied to this.

                        dutchy101 Please get a drop kit as the GH and KH readings are what you require.

                            LMSC

                            I’ve alredy got one - just need to pull my finger out and perform the test haha.

                                dutchy101 Would like to know the pure RO readings as the mineralised total hardness readings seem on the higher side.

                                Please do sample it on 20 ml or 40 ml water for better accuracy. Obviously, you will standardise for 5 ml. :-)

                                Thx

                                  mathof2 Oh good point above. Did you follow the instructions and use a 5ml sample or get a 20ml sample for better accuracy?

                                  Also did you stop the test at the first sign of colour change or continue until there was a “bright” colour? The former is what you need to do.

                                      Rob1 Oh good point above. Did you follow the instructions and use a 5ml sample or get a 20ml sample for better accuracy?

                                      Also did you stop the test at the first sign of colour change or continue until there was a “bright” colour?

                                      I drew off about 40mm into a beaked measuring jug, and poured 5mm samples from that into the supplied test tubes.

                                      I stopped soon after the first faint sign of colour change, but perhaps I went a drop too far.

                                      I will re-do the tests on the coffee infusion samples and do new ones on the pure RO water, and report back.

                                      Thanks to all for your assistance.

                                          mathof2 Rob1

                                          Here are the latest measurements (ppm):

                                          RO water: GH 35.8 (2 drops); KH 35.8 (2 drops); total TDS 46 (meter)

                                          Coffee minerals: GH 89.5 (5 drops); KH 53.7 (3 drops); total TDS 98 (meter)

                                          Tap water: total 199 (meter)

                                          Question: could it be right that the total measured-by-meter TDS of the samples is greater than the total minerals in the samples measured by drops?

                                                mathof2 Question: could it be right that the total measured-by-meter TDS of the samples is greater than the total minerals in the samples measured by drops?

                                                TDS (ppm of everything in the water, as ion) and GH (calcium and magnesium only, multiplied by known factors)/KH measurements (ppm as CaCO3) are not in common units, forget the TDS.

                                                    mathof2 I haven’t and you don’t need to either 😀

                                                    Just stick to the meaningful units.

                                                    GH & KH relate to scaling potential and alkalinity (KH) in the water, KH also affects perceived acidity in the coffee produced (more alkalinity/KH = less acidity).

                                                    TDS is anything in the water, organic & inorganic, much of which has little to no effect on what we are interested in.

                                                    Course completed. Look at it as ingredients rather than ‘science’.

                                                      mathof2 Ok what I’m trying to understand here is what the RO water is. 35.8mg/l GH/KH seems high.

                                                      So as has been touched upon above a 20ml sample will give better accuracy. With a 5ml sample, when the colour changes with two drops you know the GH/KH is somewhere over 17.9mg/l and below 35.8mg/l (range between drops is 17.9mg/l). With a 20ml sample the range between drops will be 4.475mg/l….so the test is much more accurate with a larger sample.

                                                      Right now your RO is 17.9-35.8mg/l GH/KH and your remineralised water is 71.6-89.5 GH and between 35.8-53.7 KH….so the infusion adding 10.8 KH might be right. Weird formulation adding only 10mg/l alkalinity to supposedly highly pure RO water.

                                                          Rob1 Weird formulation adding only 10mg/l alkalinity to supposedly highly pure RO water.

                                                          It would only be highly pure if a DI resin filter was used (no mention of that).

                                                            Now I understand what is meant by a 20ml sample (each drop to be multiplied by 4.475O). I’ll use that method tomorrow and post the results.

                                                            I have a worry that the RO water is being contaminated by a leak from the remineralisation bottle. The TDS readings on the RO water went up when I first added a remineralisation bottle to the machine, and have stayed up. I know Skuma has identified such leakage as a possible problem. But given that such leakage would be only of wanted minerals, I don’t know if it matters.