A district council is installing dozens of isolation valves on a water system to help solve the mystery of massive water loss.
Ruapehu District Council says 40 isolation valves will help identify leaks or high points of use, including possible illegal commercial water intakes from Ohakune’s reticulated network.
The council is also considering using thermal imaging to find underground leaks on private properties as the holiday town battles to stem the unexplained loss of 720,000 liters (720 cu m) of water every day from the network.
In June last year, the council said the volume of water missing was equivalent to filling the township swimming pool two and a half times a day.
Reducing unexplained water loss was essential to manage future demand – including the growth of services in new residential developments – and to avoid preventive boil water advisories.
Boil water advisories are issued when the council is unable to provide water that meets drinking water standards. This is a particular problem during periods of heavy rain and busy school holidays when poor raw water quality reduces drinking water production and there is not enough treated water stored to handle the high demand.
Infrastructure services manager Stuart Watson said reducing overall water demand and reducing leakage losses from 20,000 liters per hour to 10,000 liters per hour would give Ohakune the best chance of avoiding a boil water advisory during these times.
It would also help meet water resource consent limits and enable the Ohakune water treatment plant to serve much-needed new housing, he said.
Chief executive Clive Manley said water savings of between 5,000 and 10,000 liters per hour had been achieved over the past year thanks to an ongoing awareness campaign. The campaign asked people to report leaks diligently because porous volcanic soils allow water to flow underground, making leaks difficult to spot.
Residents were also offered free plumbing worth $200 per job to fix household leaks and drips.
“So far, 48 people have opted in to free plumbing and we’re delighted with the response,” Manley said.
The council’s water contractor Veolia has repaired all network leaks discovered as a result of the free plumbing offer and all other known water network failures have been resolved, he said.
“To achieve half the required water saving is important, but we still use more water than we should in theory.”
Possible informal water withdrawals over several years
Manley said the council is now investigating the possibility of informal catches or illegal commercial uses.
“We are working methodically to identify these informal outlets where people have tapped into the pipes and are taking water that we are not aware of. Some practices may have been in place for years.
“We need to know who is taking the water. We will then talk to those users and work with them to regulate the water taking. We’re not going to shut down businesses, it’s more about understanding who is taking the water. “
Manley said the council is carefully working on a strategy to target illegal commercial use at network edges.
“We asked water staff to scour rural/outdoor parts of the network for unusual connections. This identified a number of practices that would consume a significant volume of water.
“These users were contacted, resulting in behavioral changes at the time. We maintain continuous monitoring of these situations.”
Isolation valves would allow monitoring of water flow in smaller areas of the reticulated network to identify what was happening in those isolated sections.
“Veolia has identified the exact locations within the network for the facilities,” Manley said.
Work did not continue immediately because water modeling was needed beforehand to plan for the development of new housing.
“This modeling is now complete and calibrated against potential new housing developments. The cost of the works has been budgeted for this financial year 2022/23 where we plan to install around 40 new isolation valves.
“This will allow us to refine and better understand demand. Based on the careful data acquired from the reservoirs, demand rises and falls throughout the night. This demonstrates utilization.”
Manley said underground leaks through private properties were a potential issue that could be explored in the new fiscal year. New thermal imaging technology could be effective in targeting this type of loss.
He said the proposed Three Waters reform had no impact on the council’s efforts to prevent the water from disappearing.
“Three Waters reform is irrelevant. We are required to manage our water well,” Manley said.
The council’s long-term plan included maintaining an accelerated work program to modernize its drinking water plants within five years. One such project was a new water treatment plant for Ohakune.
“Producing drinking water is expensive and repairing large water losses directly affects the capacity of the plant we have to build and the amount of water we need to produce.”
Manley said there were no plans to introduce water meters for domestic users.
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