Water Alkalinity measurements after boiling

[mabrungard]

As many know, boiling a water with high Temporary Hardness can be used to reduce hardness and alkalinity. The reported practical lower limit for alkalinity is somewhere between 50 and 65 ppm (as CaCO3). I was wondering if any brewers have performed alkalinity testing of their post-boiled water and they can confirm or negate those reported limits?

Thanks!

 

[keith1664]

Suffering as I do from very hard water you've got me interested enough to try a little experiment, once it's cooled and settled out I'll let you know.

 

[keith1664]

The results are in, though how accurate they are?

There were 2 things I wanted to check, how long to boil for and how low (high?) the alkalinity got.
I measured my tap water at 262.5 mg/l CaCO3, then put it on to boil. I then took samples at 5,10,15,30 and 45 minutes after it reached boiling. The samples were left for 3 hours to cool and settle. I then measured them again using a salifert carbonate hardness / alkalinity test kit.
The 5 minute sample measured 68mg/l initially, it then went blue again and required another drop to bring it back to pink, making it 70 mg/l.
The 10 minute sample came in at 39.5mg/l and again returned to blue, ending up at 45mg/l.
All the other samples came in at 39.5mg/l and stayed there.

I'm assuming the reason the first 2 samples changed back to blue was that there was still some chalk in suspension which went back into solution when the test was carried out, maybe the particles had grown after subsequent boiling so had dropped out in the other samples.

Conclusion - yes you need to boil the water for 15 minutes to remove temporary hardness, boiling for longer won't reduce it any further.
Secondly I probably need a more accurate measuring method but it seems our figures are reasonably close.

 

[mabrungard]

Yes, even though you can't see the chalk particles, there is a possibility that they were still suspended in the 'clear' water. So that could explain the result.

Thank you very much for your experiments. By the time the water reaches a boil, the solubility of the CO2 is very low. But it takes a bit of agitation to get that gas out of the water column. Either a brisk stirring or brief, rolling boil will get that gas out. Extending the boiling time should not create a significant difference in the resulting alkalinity. It's good to see that your results confirmed that.

I think the range reported for the effectiveness in removing alkalinity by boiling has to do with the vagaries in how the water is handled after the boil and the degree that CO2 is redissolved in the water. It sure looks to me that a brewer could achieve the 50 ppm alkalinity value with good practices.