A lot more expense than simply paying for tanks

October 21, 2005

A lot more expense than simply paying for tanks

Toowoomba City Council supports the installation of rainwater tanks, making it compulsory for all new developments to fit tanks and offering rebates for residents who retrofit them.

However, claims made by Dean Cameron in the Chronicle on Thursday, that installation of 30,000 rainwater tanks to homes would be a “cheaper and more effective” solution to Toowoomba’s water shortage problem are naïve according to Mayor Dianne Thorley.

“Council has already looked into the costs associated with installing rainwater tanks and there is a lot more expense than simply paying for the tanks,” she said.

Costing of the option was undertaken as part of the “Water and Wastewater Strategy Study for Toowoomba and the Surrounding Areas”.

Costing was based on 10,000 litre tanks, smaller than those proposed by Mr Cameron, and included pressure pump and slab, plumbing connection to toilets, hotwater system, laundry tap and one external tap – it does not include costs associated with alterations to roofs and landscaping.

The total estimated cost was $5,000 per property, for 35,000 properties, a total of $175 million.

The provision of recycled effluent to supplement laundry and outside water use, as suggested by Mr Cameron, would require the installation of dual reticulation.

Water for dual reticulation needs to be treated to at least Class A+ (equivalent to 4 star) standard, due to possible cross contamination and the high probability of human contact with the water.

The estimated cost of an appropriate treatment plant is $10m.

This would also require the digging up of every road to lay new pipes, at an estimated cost of $175m.

This figure is based on the replacement value of our existing water reticulation system and is conservative because it does not take into account additional costs associated with working around or relocating existing services such as gas, electricity and telephone lines, nor restoration of roads.

Council would also need to install new parallel plumbing to each property because we cannot allow interconnection with the potable water supply. The estimated cost of this would be $5,000 per property, a further $175m.

The total estimate for rainwater tanks is $535m and this can only be seen as conservative.

Tanks will also not be able to provide enough water to substitute regular supply to homes.

This is because at least 50% of household water, or 245 litres per day, could not be served by recycled water; for apart from drinking, things such as showers, the kitchen sink and washing machines which require five star water.

According to figures from the “Water and Wastewater Strategy Study for Toowoomba and the Surrounding Areas”, a 10,000-litre rainwater tank can only reliably supply 70 litres per day, clearly inadequate for regular supply.

Cr Thorley said it was important for people to realise that there were two costs involved for any option, the upfront or establishment cost and the ongoing supply costs.

“The ongoing maintenance costs of rainwater tanks and electricity demand of an additional 35,000 pressure pumps cannot be glossed over,” Cr Thorley said.

“The $68 million establishment cost for Water Futures will be offset in part by the State Government and hopefully also by the National Water Commission.”

“The installation of rainwater tanks would not be subsidised by state or federal governments and the cost burden would have to be shouldered by the rate payer.”