JimmyP ‘Alkalinity’, is what they used to call ‘Karbonate hardness’ (KH), or temporary hardness. It’s basically the bicarbonate value in mg/L multiplied by 0.8 to give the value as CaCO3 (this is the scale used widely in the water industry).
It’s not directly relatable to the pH (hydrogen ion).
I didn’t say UK tap water was uniform, ground water is very widely varied, but the areas of soft water tend to be in the West & (igneous rock) & more sparsely populated. Chase spring is roughly around the average at 140mg/L total hardness, 120mg/L alkalinity, many folk (like me) will have water this hard, or harder, coming out of their tap.
