Brewing with rain water?

[David R]

On Monday I finally got around to putting down the first brew since moving to our new house, JoKings Epic Pale Ale recipe. At this state I'm just using extract + grains (may step it up to all grain some time in the future), and half way thru the boil in suddenly dawned on me that we're now on roof/rain water supply which is incredibly soft and has very little mineral content (less than 10ppm TDS and almost unmeasurable hardness). Not sure why it hadn't occurred to me earlier given that my other main hobby is keeping tropical fish (which being from the Amazon are thriving in the soft water) as I knew what the tap water was like, I just hadn't considered it in terms of brewing....

So I guess I'll have to wait and see how this one turns out, but in future is there anything I should be adding to the water prior to brewing to make up for the lack of mineral content? From the little I've read so far I believe the pH of the mash (if using all grain) is something that needs to be correct, but just using extract will the soft water adversely effect my beer or am I worrying about nothing?

Cheers

David

[Brett Soanes]

you dont need to worry about it if do extract, the extract brewer in theory will have used the correct water when making it. in my opinion softer water should be better for extract

brett

[Grant R Baker]

According to brewers from my fathers days in the WWII Airforce training or other old school brewing books you want to add Salt and Epsom Salt (magnesium sulphate) and also Calcium sulphate (to lower ph) or Calcium carbonate (baking soda, to raise ph).

 

I would just start with the first two if your are worried about it. Have flick around on the interweb but I think you need about 5grams per 23litres for Epsom salts and maybe the same for normal salt (maybe a bit less).

[Stefan]

It's not a good idea to just throw salts in willynilly. It's best to use something like this calculator;
http://www.brewersfriend.com/water-chemistry/
Or if you don't have a collection of salts to work with I would suggest just starting with a teaspoon of calcium carbonate and one of calcium sulphate (pretty easy to get these from homebrew stores). I live on waiheke and brew with rain water. The first two brews I put down I used the same malts and hops but added these salts to one and not to the other. No salts meant no flavour and the yeast didn't drop either (yeast need calcium).
Whatever you do, don't put table salt in. It'll be iodized which will give an off flavour (best to get your clouride from CaCl2). Happy salting!

[David R]

Thanks Stefan, I already have the Calcium Sulphate (bought from the brew shop to prevent pH of aquarium crashing, still somehow forgot about it for the beer in the excitement of brewing again...), will get some Calcium Chloride before the next batch too.

[David R]

ps. is there any point in adding some to the brew I have fermenting now, been going for a week today? Probably not?