$21m bill to stop backflow
Commercial and industrial businesses in Christchurch will collectively have to pay more than $21 million for measures to prevent backflow from their properties polluting drinking water.
About 9100 businesses will each have to spend an average of $2000 to install special devices, though costs could be as high as $16,000 for those with larger water connections.
An audit last year found about one-third of commercial and industrial water connections in the city had inadequate means to stop backflow.
The requirement is only likely to affect industrial businesses that could potentially pose a hazard, rather than low-risk properties such as offices.
Preventing the problem is a key pillar of the Christchurch City Council’s water safety plan, and is necessary for chlorine to be removed from the drinking water.
Under new government guidelines the council’s latest risk assessment of the current level of backflow prevention found it to be unacceptable.
Backflow happens when water flows backward from a property and into the public drinking water supply network. It can happen when pressure drops, causing water and potentially chemicals and contaminants to be sucked back into pipes.
‘‘Backflow is one of the biggest risks to our drinking water and can seriously affect the quality and safety of our water, potentially causing serious illness, injury or even death,’’ council water boss Helen Beaumont said.
‘‘We’re committed to supplying safe, high-quality drinking water for everyone in Christchurch and to make sure we can keep doing that, we need to ensure backflow doesn’t happen.’’
Backflow prevention devices are a legal requirement for many commercial and industrial properties, typically registered during the building consent process.
But an audit of more than 10,500 commercial sites for which the city council had no record of backflow prevention found 32 per cent had inadequate measures in place.
One in 20, or 475 water connections, were found to have such poor prevention that it posed a high hazard of microbial contamination.
The council has already installed about 40 devices to avoid the need to re-chlorinate parts of the city where the disinfectant has already been removed from the water supply.
Health laws allow the authority to install a backflow prevention device on the public side of a property’s water connection to protect against contamination – and to recover the cost of doing so from the owner, along with bills for testing and maintenance.
Owners will be able to have them installed on the private side of their property’s boundary but will have to pay $430 for a building consent, a process which is being fast-tracked.
Annual testing and maintenance will add another $150 to the bill. Where installation tops $1000, owners will be able to get help to manage paying for it.
The council is spending millions of dollars to bring the water supply network up to new Ministry of Health standards for assessing risks to drinking water.
Last year it unveiled plans to use acoustic sensors to help detect leaky pipes, and for smart meters that would identify network problems and improve efficiency.
About 20 per cent of Christchurch’s water is currently free of chlorine, with most of the rest being treated with a low dose at 0.2 parts per million, which is a fifth of the level supplies were first treated with when it was brought in two years ago.