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Water hardness/softness: How soft is soft enough?

1. I have soft lake water that may not require further softening when used in the Londinium. With these figures in mind (from municipal water system’s own analysis), would I be wise to use a softening filter or definitely not?

Hardness: 12.0 (as CaCO3)
Hardness: 0.88 (as CaCO3) (grains)
TDS: 49.0
Alkalinity (CaCO3): 20.0
Calcium: 4.0
Magnesium: 0.46
Iron: 0.05
Potassium: 0.39
Sodium: 14.0
pH: 7.3

2. If I wanted to occasionally use Third Wave Water (or homemade equivalent) with distilled water, would that cause any more or less potential for scale buildup than using local water supply?


  • hi there

    it appears as though you have very nice water

    based on the data you provide above you definitely do not want to soften your water further (i.e. do not use the softening filter that we supply with the machine) or the level probe will become unreliable, by which i mean sometimes it will not sense that the boiler needs refilling and other times it may not detect that the boiler has reached the max fill level and to turn the pump off

    the precipitating compounds in your water are a subset of your TDS value, which is only 50ppm, so we know the total of the precipitating (scaling) compounds in your water can not not exceed 50ppm, which is completely acceptable as an upper limit

    as a rule i think you want the TDS value as high as possible, but the total of the scaling compounds (calcium carbonate and magnesium carbonate) should not exceed 70ppm

    in your situation you definitely do not want to use the softening filter that we supply with the machine

    kind regards
  • Very reassuring & informative to have this response & to know scaling won’t be an issue in the machine, thank you!

    If I’ve fully understood, you are also saying I could even safely increase the mineral levels a bit for flavour improvement, yes? (as long as I keep them under a total 70ppm) Good to know this as well!
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