Ian how true, we don't want knee jerk reactions, what we need is Federal money, as in the Hawke Govt days when they built the mighty Burdekin Falls Dam in North Queensland, while we are at it we could use some extra Howard money to put hyrdo electric power stations on all suitable dams, so that we have complimentry power, or is that too sensible, logical and so should go to a committee.

Toowoomba City Council was promised $46M of Federal and Queensland Governments money ($23M each) for its proposed water recycling plant. Both Governments accepted the Council’s rejection of rainwater tanks as an option for the region’s future water supply. The Council estimated that rainwater tanks fitted to existing houses in Toowoomba would cost $5,000 and yield 25KL from 9KL of storage capacity. Neither the Federal or Queensland Governments questioned the Council’s data.

In reality, the cost of supplying, installing and plumbing (including with pressure pump) a 5KL rainwater system for an average house in Toowoomba is under $3,000 provided all houses are supplied to achieve cost-reducing economies of scale.

In the 12 months to 30 June 2006, there was 603mm of rainfall in Toowoomba. This would have yielded 59KL of water for an average Toowoomba house with 150M roof area, collection from all downpipes and use of rainwater for hot water, laundry, toilet flushing and outdoors. A 5KL system would have overflowed by about 29KL during extreme rainfall events. As part of the plumbing package, an automatic switching valve is installed for returning the household to mains water the instant the tanks run dry, and back to tank at the next rain event.

The reason why rainwater tanks are not a significant source of water supply in Toowoomba is because Queensland Government policy throughout the 20th century was to discourage them. 29% of non-capital city households in Queensland have rainwater tanks but only 5% in Brisbane.

Now, the State Government wants all new houses in Queensland to use rainwater tanks. The Government considers that installing rainwater tanks in existing houses is too expensive and therefore the law only applies to new houses and major renovations.

However, if all houses were required to reduce mains drinking water consumption by 40% at point of sale, with rainwater tanks deemed to comply, there would be a significant drop in the cost of installing rainwater tanks in new houses. All house owners – new and existing – would benefit.

The Federal and Queensland Governments do not express an opinion on this proposition.

Greg Cameron

I think the main theme of the article is sensible and that there will be an impact if councils strictly adhere to the rainwater tanks requirement.

It would be interesting to redo the calculations with some less optimistic assumptions. When you say most councils is that 51% of councils representing 51% of the potential new residents? When you say that they must have a tank does that mean that a 1000 Litre tank will suffice to meet council requirements or must they have a 13,500 Litre tank? Is it always true that a resident who collects 13,500 Litres uses all the 13,500 Litres before he uses mains water or does he sometimes just prefer to use mains water for cooking and washing and let the tank water be used for flushing the toilets and watering the garden. Does the council requirement extend to apartments and townhomes where they don't have space for a big tank or sometimes any tank at all?

Is there any data on reduction in mains water usage after the start of the rainwater tank requirement? If these regulations have been in for a few years it would be interesting to see how much impact on the total water usage they have had.

Editors - In future please use ML for MegaLitres not Ml. It is much easier to interpret.
19.5 ML/day – 2.015 ML/day = 19.45 ML/day not 19.35 ML/day. It doesn’t make any difference to the general argument, but its good to add up correctly.

The Australian Bureau of Statistics has collected and published detailed data on an estimated 24.9 million megalitres of water consumed in Australia in 2000-01:

• Agriculture accounted for 67 per cent

• Households nine per cent

• Water supply, sewerage and drainage services industry seven per cent

• Electricity and gas generation industry (excluding hydroelectricity) seven per cent

• Manufacturing industry four per cent

• Mining industry two per cent

• Other industries three per cent

Water Tanks may well help the 9% of water used by households but will do very little for the legitimate needs of agriculture. This article does not address the major problem.

Greg,
If I could afford a rainwater tank I would fit the largest one possible for urban useage, however if the government made it mandatory, I would have to sell myself sexually to get the required income, a prospect I wouldn't look forward to.

Not everyone is in the financial position to install rainwater tanks even though they would love to do so. We all pay tax, even we pensioners pay G.S.T.in a critical situation on the driest continent on Earth with the Howard Government having a $10.8 billion budget surplus, is it not a reasonable request that it either build dams, as Hawke did, or subsidise to a large extent rain water tanks, for those who are prepared to install but have no cash up front?

The key point is that most, if not all councils are mandating water tanks and when faced with this mandate, the builders are going for maximum benefit to maximise the marketing advantage.

The average house now has 250m2 of roof area so 600mm in Toowoomba will equal 150,000L of captured water.

So the key point stands. The market for mains water is already shrinking but new long term supply infrastructure is being justified on the basis of an expanding demand. And this will destroy the economics of even the existing infrastructure.