Crisis? What water crisis?

When I tell you that in Brisbane there is no water crisis, and not even a drought, you could be forgiven for checking my medication. But those who didn't come down in the last shower may recognise the debate being shaped, not so much by a conspiracy but, rather, a loose coalition of the well meaning, with opportunists, excuse makers and outright departmental shonks. And as is often the case, the most important attributes of the truth, the hard numbers, didn’t even make it onto the interchange bench.

We have the premier saying, "we're doing our best but I can't make it rain". Others advise that, "even 50 water tanks are no use if it doesn't rain" and before long we saw the first evidence of policy panic with mean-spirited sanctions on frail and aged people. And silly, costly and ineffective measures like mandatory pool blankets as the first indication of a search for scapegoats. Soon even the most sensible start to wonder if the global warming Bunyip has teamed up with the four horsemen of the apocalypse.

So let’s put this in perspective. My family of five’s annual household expenditure is about $40,000 of which $160 is the cost of water. It amounts to 0.4 of 1 per cent or, dare I say it, two fifths of sweet FA. And that is the proportion of our thinking time that should reasonably be allocated to the subject. Our problem is that the government-owned supplier of this water is advising us that it is unable to deliver the desired product in the volumes required or at the times we require it. And as anyone from a business background will tell you, those that cannot deliver the goods often waste excessive amounts of your time with endless excuses as to why “their” crisis must also become “your” crisis.

Furthermore, this supplier has confirmed its intention to raise the price for this product that it will deliver less of and with less reliability. So what would an even half-competent manager do? He could check the alternative suppliers, or he could bring the function “in-house” and by-pass the incompetent, monopolistic middleman. He could invest in his own value chain, with a water tank or two.

The first thing to do is check the availability of the raw material. At the Bureau of Meteorology he would be surprised to learn that there is no shortage of this raw material. The rainfall data makes it clear that the past 12 months has been far from drought. From May 2005 to April 2006, Logan had 1,245 mm, 18 per cent above the average 1,058mm. Strathpine in the north had 1,214mm.

So what have these people been going on about? They passed up an opportunity to diversify their catchments more than a decade ago and now want to pass on the higher costs to customers. And their two largest storages have had a bad year. Wivenhoe had only 550mm in the past year against an average of 1,007mm. Interestingly, the alternative storage at Wolffdene, the right dam, in the right place, at the right time, but vetoed by Goss, had 1,127mm. Clearly, there is a crisis of management competence, not a water crisis.

Councils cannot stop you using other sources but you must remain connected and pay the fixed annual fee of $110. This allows you to use as much water as you can collect in your own tank and only take their water as a last resort. If you are not connected you would have to cover any shortfall by trucking in water at ten times the cost, as some acreage dwellers and farmers sometimes do already.

And never mind the “health concerns”. More than 15 per cent of Australian households already use tank water, including 37 per cent in Adelaide, and there appears to be no variation between the two in the incidence of water borne ailments. It is a remarkably convenient urban myth that furthers the interests of the public sector water mafia. You are more likely to get sick from your refrigerator, but if managing a fridge is beyond you then, by all means, don’t get a water tank.

A water tank allows you the sweetest pleasure of having as little as possible to do with a whole cohort of bozos who want to share their problem with anyone gullible enough to put up with it.

You’ll save money and make a profitable investment in your own home.

Which tank? How much will it cost?

The optimum tank for your situation depends on your average use, your roof area, your rainfall, your catchment efficiency, your storage capacity, your overflows and your shortfalls. We compiled a series of spreadsheets to make sense of it all and discovered that investing in the right storage capacity is one of the lowest risk, highest return investments you can make.

The average household uses 700 litres a day or 255 kilolitres a year at a cost of 94 cents/kL or $240 a year. If that money was used to pay off a mortgage at 7 per cent interest over the 25 year tank life, then a bank would give you 11.65 times the annual payment. But in this case you are not investing for an additional benefit but simply replacing an existing outlay. Capturing your own expense is one of the lowest risk investments you can make. So it is more appropriate to use the official cash rate of 5 per cent which also matches the average yield of a rental house. And this would set the capital value of your $240 water bill at 14.09 times, or $3,380. Spend more and your tank water will cost more than council water.

That is, until the next price increase. Projected to be 6 per cent a year, they will double in 12 years from $0.94/kL to $1.90/kL and this differential will improve the rate of return on your investment accordingly. But even without these savings, the largest 27,000L polytank will give you $300 change from your $3380 break even point. But this is serious overkill for a house connected to mains water.

The average roof is 250m2 and each millimeter of rain makes a litre of water on each square metre of roof. And all of it can go into the tank. Your existing supplier, on the other hand, has trees and pasture in their catchment so only 5 per cent of their rain will flow into their dam. And their storage has no roof so half of that will evaporate to give a net efficiency of 2.5 per cent compared to your 100 per cent.

Without recycling, the average Brisbane household needs only 1,020mm of rain (89 per cent of average) to supply all of their water needs. The spread of both rainfall and water use enables smaller tanks to be refilled many times whereas the public water system relies on one big storage that is only filled every five years. And this is a major contributor to public water inefficiency. The annual cost of your tank is spread over the number of times it fills each year, many times its own capacity.

All other factors being equal, the smaller the storage, the more times it will be filled and the lower the apparent cost of a captured tank full. But don’t go out and buy the smallest tank available. The smaller the tank, the sooner it will overflow. A 1,000 litre tank costing $430, connected to 250m2 of roof will overflow after only 4mm of rain so most of those valuable summer storms would be wasted. The tank may fill up 264 times but the projected cost of only 12 cents/kL would be illusory because only a small portion of it would actually come out of the tap.

A 22,000 litre tank costing $2,700 would need 88mm to fill and it would lose much less to overflow. It would only fill 12 times a year to produce a projected cost of 72 cents/kL. But even this size will still lose 1.5 tanks to overflow in an average year and will need a 1.12 tank top up from the mains in a dry season. And obviously, the supply of your own water will drop in a bad year and the cost of the tank will be spread over fewer full tanks. In a year with only 81 per cent of average rain (857mm) the average cost of water, including the additional purchases from the mains, will rise to 89 cents/kL. In an above average year like the past 12 months with 1245mm of rain, the overflow will be greater but the amount drawn from the mains will be lower and the average cost will fall to only 82 cent/kL.

Interestingly, once you have installed an adequate storage capacity there is very little sense in adding lots of additional water-saving devices as these will only reduce the total volume of water against which the cost of the tank is defrayed. These gadgets are fine in very low rainfall zones but on the coast they can make your tank water a lot more expensive than mains water. And let’s face it, it is your water from your roof, so feel free to use as much of it as you like, as you like. Go on, you can even hose your driveway, it will only go down the drain if you don't.

The optimum mix of limited mains extraction in dry times and limited overflow in wet seasons was met by a 13,500 litre tank costing $2,050. This would need additional outlay on foundations and plumbing but this would be covered by the $850 worth of council rebates. Beattie has recently announced a $1,000 rebate but details are still unclear. But even under the old rebate it would deliver an average water cost of 69 cents/kL in a normal year and 74cents/kL in a dry year. And only 13 per cent of total household use would be drawn from the dams, enabling them to perform their proper role as a supply of last resort to an urban community that has taken all reasonable steps to help itself before putting its hand out for a public service.

Our much-maligned farmers have been doing it for decades.