Reducing the unexplained water loss was critical to managing future demand – including servicing growth in new housing developments – and to avoid precautionary boil water notices.
Boil water notices are issued when the council is unable to supply water that meets drinking water standards. It is a particular problem during periods of heavy rain and busy school holidays when poor raw water quality reduces drinking water output and not enough treated water is stored to manage heavy demand.
Infrastructure services manager Stuart Watson said reducing overall water demand and stemming loss through leaks by 20,000 litres per hour to 10,000 litres per hour would give Ohakune the best chance of avoiding a boil water notice during those times.
It would also help keep within water take resource consent limits and allow the Ohakune water treatment plant to service much-needed new housing, he said.
Chief executive Clive Manley said water savings of between 5000 and 10,000 litres an hour (5m3-10m3/hr) had been achieved in the past year through an ongoing awareness drive.
The campaign asks people to report leaks because porous volcanic soils allow water to flow away underground, making leaks hard to spot.
Residents are also being offered free plumbing to the value of $200 per job to fix household leaks and drips.
"We've had 48 people taking up the free plumbing so far, and we're pleased with that response," Manley said.
Council water contractor Veolia fixed all network leaks found as a result of the free plumbing offer and any other known failures within the water network had been addressed, he said.
"To achieve half of the required water saving is significant but we are still using more water than we theoretically should be."
Manley said the council was now investigating the possibility of informal takes or illegal commercial use.
"We are methodically working through identifying those informal takes where people have tapped into the pipes and are taking water that we're not aware of. Some practices may have been in place for years.
"We should know who takes water. We will then have discussions with those users and work with them to regularise water take. We're not going to close down businesses – it's more a case of understanding who is taking the water."
Manley said the council was carefully working through a strategy to target illegal commercial use at the extremities of the network.
"We had water staff walk around the rural/outer parts of the network looking for unusual connections. This identified a number of practices that would consume a significant volume of water.
"These users were spoken with, resulting in behaviour changes at the time. We are maintaining ongoing monitoring of these situations."
Isolation valves would enable the control of water flow across smaller areas of the reticulated network to identify what was happening in those isolated sections.
"Veolia have identified the exact locations within the network for the installations to take place," Manley said.
The work did not proceed immediately because water modelling was needed beforehand to provide for a new housing development.
"This modelling has now been completed and calibrated based on the potential new housing developments. The cost of the work has been budgeted for this 2022/23 financial year where we plan to install approximately 40 new isolation valves.
"This will allow us to finetune and better understand the demand. Based on the minute data acquired from the reservoirs, the demand ramps up and down throughout the night. This demonstrates use."
Manley said underground leaks through private properties was a potential problem which could be explored in the new financial year. New thermal imaging technology could be effective at targeting this sort of loss.
He said proposed Three Waters reform has had no impact on the council's efforts to stop water disappearing.
"Three Waters reform is not relevant. We are required to manage our water well," Manley said.
The council's Long Term Plan includes maintaining an accelerated work programme to upgrade its drinking water plants within five years. One of these projects is a new water treatment plant for Ohakune.
"Making drinking water is expensive and fixing large water losses directly affects the capacity of plant we need to build and how much water we need to make."
Manley said there were no plans to introduce water meters for domestic users.
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