Drinking rainwater and staying alive

Spring on the way, and spring in us if we choose it

Fellow water imbibers: I’ve been asked this lengthy, well-informed and valuable question:


I’m planning a new house with two 20,000L rainwater tanks, possibly of stainless steel, and I’m trying to decide what roof and gutter and downpipe materials to use.  I’ve read the reports of Mirela Magyar’s studies on metal contaminants in rain water tanks in Melbourne, and I’m reading your book Sustainable House (2010).

Do you have any opinions on the best roof materials to minimise health problems (and also to minimise embodied / lifecycle energy)?

In one of Magyar’s studies, 5 out of the 7 tanks with zinc levels higher than recommended had a galvanised roof.  I wonder if these tanks had first flush diverters, and if not, could this have minimised/eliminated the problem?  (I understand that inorganic contaminants tend to attach to particles in sludge.)  Is your roof galvanised?  How old is it?  Do you know if older galvanised iron would lose more or less of its zinc into rainwater than new?

I’m also considering zincalume, which I expect would last longer, perform better thermally, and be cheaper, but I imagine that both zinc and aluminium could end up in the water from it.

And I’ve considered colorbond, which should also last longer and, if white, perform better thermally, but I’m concerned that when it starts to deteriorate (I think it’s warrantied for 20 years), contaminants from the flaking surface, and its primer (containing strontium chromate, whose dust is a suspected carcinogen) and the underlying metal (zincalume) could end up in the rainwater,.

I’d be grateful of any thoughts, answers and references to help me decide.’


Let’s cut to the chase.


In 200 years of western culture no one has died drinking rainwater in Australia.


About 3 million Australians drink rainwater every day.  We’ve drunk it here in this household, , we one to four folk, for 15 years and most damage done to us has been from bad whisky, too much ice cream and too much food.


Now, to the details.


I go for Colorobond white or pale every time; it’s accredited under the standard that vets products suitable for harvesting rainwater: AS…..

As wells as giving long term clean, healthy water it reflects light and heat and cools the house or office below.

See, for example:

My roof is over 20 years old.  Rusty, corrugated iron.  Water quality here meets National Health and Medical Research Council 2004 Guidelines: and see,



The key to my clean water is the first flush which diverts the first dirty water from the roof to the garden before the rainwater goes into the tank.  Design, product and other details are in my book, Sustainable House:


May the rain be with you and upon you and within you, go you good thing, Mother Earth





One Response to “Drinking rainwater and staying alive”
  1. Simon says:

    It is a well known fact that a Gap in general and dental health divides our nation, and the statistics show this clearly. What the statistics don’t show as clearly is the difference in consumption of sodium, chloride, magnesium and calcium caused by the different water sources from City to Country.

    Most will already know people drink more rainwater in the Country but many don’t know the rainwater is acidic and low in magnesium and calcium.
    Most know people drink ground water in the City but may not know magnesium and calcium are at higher levels and the water is alkaline.

    Both City and Country people eat the same foods but the higher magnesium diet is why the City people consistantly live longer and have less problems.

    The only obvious difference is the Country people have less magnesium and calcium in their diet and the end result is more depression, heart, dental, diabetes and dental….

    ADWG 2011 Quote “There is some indication that soft water, with a hardness of less than about 75 mg/L, may adversely affect mineral balance”
    This is best described as very slow dehydration that eventually becomes metabolic acidosis and can take anywhere upto a couple of generations in a cool climate for any symptoms to even begin to appear & much quicker in a hot climate.

    But if you read the ADWG disclaimer it is clearly still your responsibility to decide to drink the water and they are not liable in anyway.

    Check youself just google WHO “Health risks from drinking demineralised water” and “magnesium and calcium minimum levels suggested in both 2006 & 2009 reports the WHO produced.

    The government rebate for the rainwater tanks is a good thing but not informing the public the water tanks are indirectly adding to the rural health statistics is not.

    Public perception is really just a guess based on another guess………

    I do not guess anymore and the above is a good enough reason for me.

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  • Michael Mobbs

    Michael is a former Environmental Lawyer who is uniquely placed to consult in four main areas:

    • Sustainability Coach and Speaker,
    • Sustainable Urban Farm Design greening, watering and cooling the cityscape, roads, parks, suburbs,
    • Major Projects Consultant Commercial and Industrial,
    • Residential Sustainability Consultant.
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