Mineral Salts In Rainwater.

[Hogan]

Having recently listened to the BN podcast on Waterganza and read through Ray Daniels chapter on the subject of 'water' I decided to look closer at the way I was using my local water in my brewing. I get my household water from the Nepean system (south of Sydney) but since commencing AG some three years ago I have caught rainwater from the colourbond roof and added 5.2 for pH balance and either gypsum or Calcium Chloride in a measured quantity but not really knowing exactly what it was achieving. I use Beersmith but did not have a clue about the water profile feature. Now I am better armed.

I downloaded the .pdf for Sydney Water catchment areas (copy below) and transcribed my catchment report into Beersmith. After doing some sample recipe comparisons (with the town water) I found that if I had the facility to use rainwater that has a reasonable pH level to start with and a low amount of dissolved salts, then it would be a lot easier to start off on that low base line and add salts to reach required style levels, rather than dilute the town water down.

View attachment 4EA3FFE3d01.pdf


I am aware that rainwater falling in different locations has never exactly the same overall content but unless you reside just outside Chernobyl the following passage from Encyclopedia Britanica may be of interest to those who catch rainwater in a reasonably clean environment and are wondering just what the ppm levels of salts are that relate to our brewing.

Assuming equilibrium with the atmospheric carbon dioxide partial pressure (PCO2) of 10−3.5 atmosphere, the approximate mean composition of rainwater is in parts per million (ppm): sodium (Na+), 1.98; potassium (K+), 0.30; magnesium (Mg2+), 0.27; calcium (Ca2+), 0.09; chloride (Cl−), 3.79; sulfate (SO 2/4−), 0.58; and bicarbonate (HCO3−), 0.12. In addition to these ions, rainwater contains small amounts of dissolved silicaabout 0.30 ppm. The average pH value of rainwater is 5.7. (The term pH is defined as the negative logarithm of the hydrogen ion concentration in moles per litre. The pH scale ranges from 0 to 14, with lower numbers indicating increased acidity.) On a global basis, as much as 35 percent of the sodium, 55 percent of the chlorine, 15 percent of the potassium, and 37 percent of the sulfate in river water may be derived from the oceans through sea aerosol generation.


Having gotten a better handle on the whole 'water treatment' aspect of brewing through the BN podcast and the proper operation of the Beersmith water profile tool, I am now a lot more confident in making salts additions to the mash and boil phases of my brewing.

Hope this helps those who use rainwater.


Cheers, Hoges.

 

[technocat]

Rain water in my tanks in Tasmania is around 6.4 it is my understanding that rain water below 5.7 is considered acid rain. We probably have some of the cleanest air and water on the planet in Tasmania.
Rain water would be influenced by the enviroment of the catchment area such as industrial effluent and as been suggested living near an large airport doesn't help for healthy rain water for obvious reasons.

 

[Midnight Brew]

hey hey,

I've heard if your water is in a safe enough level of minerals and ph level you can boil your rain water and use it as long as you mix it with half tap water to equalize it out. Not sure if this is true but just a suggestion.

Dicko

 

[katzke]

Based on what I have read posted here rain water for brewing is basically a blank slate. The big exception comes from how it is collected and stored.

The big question comes when you try and figure out what to add to the water for brewing. Most if not all of the water profiles I have seen are suspect at the least. The best info can be gleaned from Designing Great Beers as well as following others additions from proven recipes. A bit of reading on the subject from multiple sources will help also. That is the only way I know to sort out all the miss-information out there on water profiles.

I am slowly working through the information I have gleaned but can not make any recommendations on profiles yet. It will likely take me several years to test them all. So far I have been please with my results so if you follow my advice on doing the learn-it-yourself approach you should not go wrong.