15 November 2011 – I’ve been asked this question by an architect:

“I’ve been drinking my rainwater for years so know a little about filtering it but when it comes to specifying the filtration for clients of their own rainwater, for even showering under I’m concerned we’ll leave ourselves open to a future claim should they believe they’ve been given the wrong advice.

I’m interested in limiting our liability with a statement on the drawings or specification of some sort.

Have you any suggestions.”

The answer is an architect is liable if they specify a product, design or material which causes harm.

If a court finds a filtration system caused harm then either or both the architect and the product supplier are liable.

In the Sydney Water “boil water” alert in 1998 Sydney Water was liable for any damage or harm its customers suffered from drinking their water.  After the alert Sydney Water had the law changed to significantly restrict its liability.  It can do that because it’s a government business with privileged access and power to have the law made to suit its business needs. Not so with architects.

Despite the legal situation the risk of a claim to an architect, engineer or other design and building person is next to nil.

Some observations about the extent, likelihood and history of risk and harm from drinking rainwater follow:

  • No one has died drinking rainwater in Australia since white people came here a couple of hundred years ago
  • Some 3 million Australians drink rainwater every day
  • The joint publication of the state and territory health agencies say rainwater is safe to drink – see below
  • Establishing that it was the filtration system which caused harm would be very difficult
  • Data in my book, Sustainable House, and on my web page, shows that rainwater monitored over several years at my house in the dirty, polluted inner city air of Chippendale is cleaner than Sydney Water
  • Most folk don’t know how Sydney Water, and other mains water sold by government monopolies, harms them; why would governments which make millions of dollars of income from these businesses tell their customers about that?  For example, when chlorine (used in mains water to disinfect it) breaks down as it sits in the pipes it becomes four “trihalomethanes” or THMs. One of these causes about 2 per cent of stomach cancers in the US where the health agencies have set a maximum level that’s half that in Australia. Oops. You breathe these THMs in when you shower or drink Sydney Water’s water. Yum.
  • A study of children by South Australian Health (Heyman et al) compared the health of those who drank mains water with those who drank raintank water.  Many of the rain tank houses had dead animals in them and gutters which had never been cleaned.  The kids who drank rain water were no more and perhaps less liable to gastroenteritis than kids on mains water.
  • Speaking of the government stalking horse, used to protect its businesses from competition and inconvenient truths, its health agencies, the one in NSW, NSW Health, advises people to drink rainwater only if they’re not connected to mains water.  There is no science to support that advice.  My data shows Sydney Water’s water, for example, has more pollution than my rainwater, particularly of THMs. In some locations the chlorine accumulates in the mains pipes due to differences in pressure and flow.
  • My rainwater is unfiltered and the data is from unfiltered samples. (Hey: it’s all in my book, Sustainable House, you’re better read than dead – read it tomorrow unbelievers.)

The joint publication of the state, territory and national health agencies says:

“Rainwater tanks can provide a relatively safe, soft, clear and odourless source of water that can be used for a range of purposes including drinking, washing, bathing, laundry and gardening.

Rainwater can be collected to supplement existing supplies or as the sole source of household water.

In Australia the use of domestic rainwater tanks has been a long standing and relatively common practice. In 1994 a survey by the Australian Bureau of Statistics showed that about 13 per cent of all Australian households use rainwater tanks as a source of drinking water. The highest use was in South Australia (37 per cent) and the lowest was in the Northern Territory (2 per cent) and the Australian Capital Territory (0 per cent)  – Australian Bureau of Statistics, 1994.

Guidance of the use of rainwater tanks, David Cunliffe, National Environmental Health Forum Monographs, Water Series No 3, 1998, p8

I only work on projects where rainwater is drunk or is the main source of water.

In only one project I’ve worked on has the rainwater been polluted and a risk to human health.

But it was serious.

There the roofing material did not meet the specification and leaked mercury into the rainwater which put the level of mercury above the level recommended for mains or town water supplies (which have a very different and much higher toxicological risk than do individual sites  due to the number of consumers and the much greater number of risks to larger, centralised systems).

The mercury was in the waterproofing used on the roof, despite a specification that that material would be fit to use in a rainwater system.  It’s a widely-used product.

Advice from a world-leading toxicologist was to the effect that despite the water having higher than recommended levels of mercury even the most vulnerable consumer of the water – a pregnant mother and her foetus – would not have been harmed.

Solutions include a notation on the drawings and specifications, and these design ideas:

  • These drawings and specifications provide for the use of rainwater for drinking and other household purposes. The use of rainwater for these purposes is said by the national forum of state and territory health agencies to be safe: Guidance of the use of rainwater tanks, David Cunliffe, National Environmental Health Forum Monographs, Water Series No 3, 1998, p8.

Where a filter is in these drawings or specifications and is installed then the manufacturer’s manual is provided to the client with these documents. The client is advised to maintain the filter according to the recommendations of the manufacturer and to consult the manufacturer or supplier or installer about any aspect of the use and operation of the filter

  • Installing a first flush between the rain tank and the rain water supply pipe(s)
  • Installing a gully trap between the rain tank and the rain water supply pipe into which sediment may be deposited;
  • Not cleaning the rain tank; research from the University of Newcastle shows the raintank forms a film which has the effect of cleaning the stored rainwater (Coombes and others).This can be a note on the drawings and specifications.

There is no law preventing rainwater being drunk in a city or town that I’m aware of.

There are some guidelines that recommend using mains water instead where it’s available but there is no science to support those guidelines – if there were the health agencies would publish it.

Everything else that’s said to contradict these assertions is myth, politics, fear, and the usual humbug that’s around and preventing sustainable use of water in this dry country.

Isn’t it interesting that the law, design and ideas for drinking, harvesting and sustaining rainwater are not taught in Australian architecture, engineering, planning and plumbing schools in the year 2011?

Nor is it taught that the most polluted air in our cities is inside a newly built house or unit or office where the off-gassing from oil and gas based materials and other chemicals is widely known to be unsafe for humans?

In fact, the furnishings, cabinetry there is far less safe than mains water.

But Sydney Water doesn’t sell furniture and so doesn’t sool NSW Health onto any competitors they might have.

Thus, the cabinetry and furniture industry flourishes, pollution and all.

(Fair dinkum:  we can chill, have a sweet glass of rain water and live well.  Full stop.)

Michael Mobbs is a sustainability coach and author (of Sustainable House now in its second edition) who advises, teaches and speaks on sustainability issues. He works with developers, governments and communities to design and obtain approvals for houses, units and subdivisions. He is based in the inner Sydney suburb of Chippendale, where in 1996 he pioneered the conversion of his inner city terrace into a sustainable house, which has now been disconnected to mains water and sewerage and is powered by solar energy. 

Michael practised environmental law for 19 years and was the consultant to the NSW Parliament Inquiry into Sydney Water and the water treatment plants in 1993. See www.sustainablehouse.com.au