Rain water chemistry

[Bellyup]

I ask the question even though the answer would seem simple.....
Are there any chemical assumptions to make when inputting rain water into some of the brewing water calculators for brewing.
For me it would be inland rain onto a Colourbond roof then into a Poly tank.
Thanks,
Bruce

 

[razz]

Hi Bruce, for my rainwater I just use the available data from the local water authority report and use those values in Brewers Friend software.

 

[Bellyup]

Hi Bruce, for my rainwater I just use the available data from the local water authority report and use those values in Brewers Friend software.

Hi Razz
Thanks for the reply
My water supply doesn’t list anything other than tap water......

 

[An Ankoù]

Hi Bruce,
I use rainwater from time to time. Let it rain for half an hour to clean the air and clean the roof. Treat the water you collect thereafter as chemically pure water. It isn't, but for brewing purposes it's good enough. Use it within 36 hours and keep it out of direct sunlight.
Great for Czech pilsner!

 

[Bellyup]

Thanks An,
I sought of thought that....... good to get another opinion.
It's great to have access to this forum and knowledge.... you guys rock!
Thanks,
Bruce

 

[Superoo]

Hi Bruce,
I use rainwater from time to time. Let it rain for half an hour to clean the air and clean the roof. Treat the water you collect thereafter as chemically pure water. It isn't, but for brewing purposes it's good enough. Use it within 36 hours and keep it out of direct sunlight.
Great for Czech pilsner!

I'm in the same situation - colorbond roof and poly tanks.

Where would I find info on how to set the water up better, if not perfect.

I've never treated water before when brewing, I do BIAB all grain.

cheers,
Chris

 

[Hallaa68]

I took data from a CSIRO publication called “New insights to the chemical and isotopic composition of rainfall across Australia”

https://publications.csiro.au/rpr/download?pid=csiro:EP125581&dsid=DS4

 

[Whistledown]

I am also in the same situation. Tin roof poly tank. I purchased a cheap TDS (total dissolved solids) meter from ebay. These are used to test reverse osmosis water filters to determine when to change the membrane. A reading of less than 30 ppm is deemed ok for reverse osmosis water quality. The readings I am getting are in the range of 7-9 ppm therefore my water can be classed the same as RO. I still filter through a carbon filter to remove any possible taint from the plastic tank liner. I then add minerals appropriate to the beer being brewed.

 

[philrob]

Before I moved 5 years ago, I brewed with tank water, and treated it the same as RO, and added appropriate salts etc to the style I brewed. Never was a problem.
As said above, it's great for brewing lagers.

 

[Grmblz]

Treat mine as if RO, tin roof concrete tank, apparently the concrete buffers the ph, my neighbour has corro tanks (plastic lined) and his ph is way too acidic for AG. I'm far south coast NSW.

 

[wide eyed and legless]

I have plastic tanks and need to get the pH down to around 5.6 for hydroponics, I dose the whole tank with 'pH Down' you can get it at most hydroponic and aquarium shops.

 

[MHB]

Treat mine as if RO, tin roof concrete tank, apparently the concrete buffers the ph, my neighbour has corro tanks (plastic lined) and his ph is way too acidic for AG. I'm far south coast NSW.

I think you might need to recalibrate your pH meter.
The odds of tank water being that acidic outside a highly polluted industrial (think Acid Rain) area are pretty low.
Concrete tanks will donate some Carbonate when they are new, but after a couple of years they should be pretty neutral, which is good because unless you need to raise the pH (very big stouts - maybe) Carbonates aren't your friend, I would choose a polly tank (or lined) over concrete. Mind you I would still want a carbon filter in line, no knowing what sort of odd plastic products would be winding up in your water and we are finding out how nasty some of then can be.
Mark

 

[Grmblz]

My pH is 5.5 according to my meter and 2 different strips (yep just re-checked it) the chap up the road had blue water after his new tanks went in, apparently it was from his copper pipes and acidic water, they had to install 100mm pipes full of crushed white rock (some sort of carbonate I guess) between his tanks and house, he doesn't brew just didn't want his copper pipes being eaten.

 

[MHB]

Typically the crushed white rock would be Marble.
I would be seriously wanting to know why the water was that acidic, natural rain water can be a touch acid from dissolved CO2 (Carbonic Acid) even down to 5.6pH.

Actually just went and did a bit of Googling on this and your, right looks like it can be a problem for poly tanks and copper plumbing - need to do some more reading.

A low cost fix would be to toss a bag of marble chips (landscaping suppliers) into the tank and monitor the pH, when it starts to fall add some more.
For brewing dissolved CO2 isn't really that big a problem, as soon as you start to heat the water up you will eject the CO2 and the pH will head back toward 7pH. Temporary hardness should go up if you treat the water with carbonate so you might notice an increase in calcium deposits in your kettle.

Interesting, my plumbing experience predates poly tanks, it was all Gal and Concrete back then. Always learning.
Mark