rain water = soft water and higher extraction rates?

I brewed this weekend and used rain water for mash and sparge. I don't have a reliable way to easily check ph. I'm curious if rain wanter (soft acidic water) aids in extraction rates. Also, have you/can I use soft water for mash and sparge then treat the wort pre boil to harden it up for better hops utilization. I'm unschooled in this part of brewing and looking for some knowledge. (I have been researching this since this past weekend but haven't found a clear answer)

Thank you in advance.

I'm specifically describing malt/ starch extraction and conversion. I had 82% efficiency up from 72%. It got my attention.

Most importantly, rain water also has very low alkalinity. The combination with the low hardness provides a low residual alkalinity that typically results in a lower mash pH than if the mash had been conducted with a higher residual alkalinity water. The lower mash pH will improve the fermentability of the wort, but I don't think that the use of rain water produced the increased extraction. The milling and the runoff duration have the greatest effect on extraction efficiency.

mabrungard said:

The combination with the low hardness provides a low residual alkalinity..

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I'm sure that's a slip. Since RA is alkalinity minus hardness/3.5 lowering alkalinity does lead to lower RA but high hardness in a low alkalinity water results in an even lower RA.

Oops! Yes, harder water would have even lower RA. That water still has relatively low RA.

So your saying the water would not have anything to do with my increased efficiency but would leave a more alkaline profile and over all higher ph? chemistry is not my strong suit.

Hume-ulus said:

So your saying the water would not have anything to do with my increased efficiency but would leave a more alkaline profile and over all higher ph? chemistry is not my strong suit.

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Yes, the water should not have had an effect on efficiency.

No, I don't think that rainwater would present a more alkaline water for brewing. Its more like distilled water with a few atmospheric contaminants. The mash pH should have been similar to what it would have been with distilled. It should not have been too high if you had some crystal or roast malts in the grist.

Even pure (distilled, ion exchanged) water has some alkalinity which depends on how alkalinity is defined. But it's about 2.5 ppm as CaCO3. Rain water can have less alkalinity than that - in fact it can be negative - and how much less depends on where the rain comes from. I'm sure you know where this is headed but rainwater often contains some nitric and sulfuric acids and always some carbonic. So rainwater doesn't have higher alkalinity than pure water - quite the opposite but the important thing is that the amounts of alkalinity/acidity are small enough that they can be neglected.

Marin and AJ,
Out of curiosity and not for argument, above it is stated that water doesn't effect efficiency. Doesn't water / mash pH effect conversion? If using rain water or otherwise treating water to achieve optimum pH, the mash is better converted, then wouldn't lauter efficiency increase?

I noticed a gain in efficiency with my system when I started adjusting my brewing water to better achieve optimum mash pH.

PlainJay said:

Doesn't water / mash pH effect conversion? ...
I noticed a gain in efficiency with my system when I started adjusting my brewing water to better achieve optimum mash pH.

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Yes, absolutely but the reason for doing it is not so much that it swings efficiency a couple of points but for the overall improvement in beer flavor, clarity, stability etc.

Depending on where you are and when you're collecting the water, you'll want to have it tested.

In the northeast, rain water can be really gnarly stuff. I've seen a lot of pollutants and acid rain come down. Not good brewing water...

Sebas83 said:

Depending on where you are and when you're collecting the water, you'll want to have it tested.

In the northeast, rain water can be really gnarly stuff. I've seen a lot of pollutants and acid rain come down. Not good brewing water...

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1+ this ^

And it really depends on the brand of shingles you have on your house and the amount of mold growing inside your downspout. Some brands of shingles can impart a tar like flavor to your brew.... not necessarily a bad thing if you are brewing a stout (lol)! :cross: