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Hi Jarryn,

I think you'd find a TDS meter handy, and also a good investment. They tell you the Total Disolved Solids (TDS) in Parts Per Million (PPM) in your water. This will give you an idea how "minerally" your water is, but it won't tell you which minerals.

A use case, if the TDS meter shows you the PPM is very low, they depending upon what beer your making, you may be able to safely assume it's a blank slate and add minerals to get close enough to the water you want. With the rainwater minerals being an insignificant contribution compared to the quantity of minerals you are adding.

Another use case, the TDS of rainwater collected fresh in a glass differs from the rainwater coming out of your rainwater tank. Could be minerals in your rain differ between showers/downpours or your roof, pipework/hoses, tank or delivery system is affecting your water. Or perhaps you didn't wash the glass, or washed it with very minerally water :)

The most handy use case is in telling you whether your water has changed. Your rainwater may vary depending on the direction of the wind, the season, whether your water came down in many little showers or one big downpour, with the seasons, etc. If there is a significant variation then it's highly likely that total mineral content (TDS) will change, not just the mineral balance. A TDS meter will tell you it's changed and by how much, in about 10 seconds.

They are cheap - less than $20, robust, reliable, have no parts needing replacement and a very, very quick and easy to use. Are they a replace a good pH meter? No, they are used for a different purpose but they are a very good complement to a pH meter and in many circumstances, can make pH testing unnecessary.

Further info:
TDS Meter: Do You Need One? - Martin Brungard - Bru'n Water
Homebrew water chemistry talk at Melbourne e Brewers club night January 2023 - Youtube

The second link is a Youtube video, seek to 4min 20sec to hear the part about TDS meters.


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