I’ve been using a Gaggia Factory 106 (based on the Pavoni) for a few years with much enjoyment. We’ve got very hard tap water, so to try to avoid needing to descale I’ve used only bottled water. I’ve always picked based on lowest ‘dry residue at 180C’ on the basis that this must correlate with low scale, but could one of the resident water experts confirm that I’ve got that right?

We’re currently using ‘Chase Spring’ from Sainsbury’s, which has dry residue <22mg/100mL, Ca <4mg/100mL, Mg<1mg/100mL, K ‘<0’, bicarbonate <14, pH 7.8. It is also very cheap (perhaps not so much environmentally, what with the plastic bottles and all). I’ve had a look through some of the water threads but haven’t really understood all the complexity. Is this Chase Spring stuff likely to be ok for the longevity of the machine? If something more commonly mentioned like Volvic, Lockhills, Ashbeck or one of the Zero plus addback solutions would be better, please could someone explain why for this novice?

    Lexicos Sainsburys have a unique method of describing water make up, by using ‘per 100ml’, rather than per litre.

    So, your dry residue is really 220mg/L high), your Ca is 40mg/L (high). Chase Spring is pretty average water regarding UK water make up, loads of people in the UK get water this bad (for coffee) straight from their tap. Don’t use Chase Spring.

    Yes, Ashbeck, Waitrose Lockhills (both these are from Armathwaite in Cumbria), or Volvic would be better than Chase Spring.

    I use Volvic/Waitrose Lockhills/BWT mg+/Zero Water remineralised with tap water, depending on what’s available & filter stock.

      Lexicos Welcome to the forum that description of calcium per 100 mg is quite deceptive, really, and it can make you think that the water’s pretty soft. The problem is that it’s normally the Calcium carbonate per litre in water, which is used to decide whether it’s soft or hard. The description you gave is for water that is 104 mg of calcium carbonate per litre.

      This is hard enough to scale a coffee machine over time. The dry residue has an impact on coffee machines but is not all hardness that reminds in the machine. The remaining dry residue doesn’t really form scale. What it can do in leaks or vacuum breakers etc is leave a residue on those.

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        Thanks very much both. How annoying that the Sainsbury’s labelling disguises the true hardness of the water. Interesting that the TDR doesn’t correlate so well with the likelihood of scaling up the machine - should I focus on the Ca and Mg instead, when they don’t give a figure for hardness?

        Is the remjneralisation purely to enhance the taste of the coffee, or is it because it’s somehow better for the machine?

        • MWJB replied to this.

          Lexicos Focus on the bicarbonate level on the water bottle, the hardness will fall in. About 50-80mg/L bicarbonate is recommended. The waters you mentioned previously are about the only practical choices in the UK in bottled water.

          Soft water, with no alkalinity can be corrosive, so you want a mineral level that controls scale and also limits the chance of corrosion.

          Water with the bicarbonate levels above should give clean tasting coffee, but if all your coffee is on the sour side, and you are sure that you are not under-extracting, then aim at the higher end of the range. (No bicarbonate can give thin, bright coffee at a normal extraction, very high bicarbonate will flatten acidity & give the coffee a heavy, dull body.

          If you are remineralising your water, you will need an alkalinity (AKA KH, or temporary hardness) drop kit to test & ensure you are on target (40-60mg/L as CaCO3).

            Thanks MWJB! Great to have your distilled wisdom. Off to Tesco’s for some Ashbeck then (or I suppose I could bring back a few bottles of tap water from when I’m next in Cumbria, as I’m there every few weeks, but presumably there would then be some issues with chlorine etc!).

            • MWJB replied to this.

              Lexicos You can do a postcode search with the water supplier next time you are in Cumbria, chlorine will dissipate if left in a non-airtight container.

                @MWJB where you’ve been using a Zero Water jug and remineralising with tap water, what TDS range are you aiming for?

                I’ve done it a handful of times and went to approx 100 on the reading.

                • MWJB replied to this.

                  Verion I’m not using TDS to target remineralisation, I use an alkalinity drop kit and aim about 50mg/L and suggest you do the same.

                  However, I have a TDS meter here and it reads 71ppm for remin Zero Water, tap water reads 254ppm. My tap water alkalinity is around 190mg/L, divide that by 3.578 and I get 53mg/L.