A couple who got their 22,000L concrete tank filled with water on Sunday only to find it empty on Tuesday now face weeks without any water at all.

The pair, who live in Stanmore Bay in north Auckland, initially assumed thieves had siphoned out their water.

The ongoing drought has left many tank owners with no water - a good opportunity to get their tanks cleaned. File photo / Alan Gibson
The ongoing drought has left many tank owners with no water - a good opportunity to get their tanks cleaned. File photo / Alan Gibson

But the truth was more mundane - their old concrete tank couldn't handle the weight of all that water and had cracked.

Victoria Coulthard posted to social media asking if anyone had had water stolen, after the tank ended up bone dry a day after being filled. No cracks were visible on the tank, which is partly buried.

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However, her partner Ryan Bailey told the Herald that after borrowing a neighbour's hose and refilling the tank 3000 to 4000 litres, the water level dropped again - pointing to a leak as the culprit.

"It had been empty for so long, the ground was so dry that the tank had moved and when you dump water in it just shocks it - so it cracked," Bailey said.

The pair had been carefully managing their supply and could have lasted another week, but with no rain forecast they had ordered a delivery.

"We were just under a quarter but we thought we'd better be safe than sorry."

They now have no water at all, apart from some thanks to a kind neighbour with a hose.

It would take another four to five days at worst to get the tank fixed, Bailey said.

With water carriers warning of waits up to six weeks, they have no idea when they will get a refill.

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"I can't really book in a tank until I know what's involved in fixing ours," Bailey said. "It could be stuffed. It could be in the bin."

The couple live on a hill. Bailey believes if they were on flat ground the tank might have been able to take the strain.

He would love to connect to mains water but says that could cost at least $22,000.

North Auckland hasn't seen rain for more than 40 days, meaning those on rainwater are desperate for their tanks to be filled. File photo / Jason Oxenham
North Auckland hasn't seen rain for more than 40 days, meaning those on rainwater are desperate for their tanks to be filled. File photo / Jason Oxenham

Concrete tank repair expert Joe Hall said many tanks in Whangaparāoa started off as baches 50 years ago.

"They were secondary dwellings and they didn't get a lot of love back in the day ... If you put in a shock load, 10,000L in 15 minutes, if a tank's weak it will split."

Rainwater, which is slightly acidic, drew lime out of the concrete or cement over time which weakened the tank and led to cracking, he said. He recommended tanks be checked or repaired every 10 years but said newer tanks tended to be better built.

Although concrete tanks could crack in any weather, people were taking the opportunity this summer to get them fixed and cleaned while they were empty, he said.

Hall - whose company Healthy Water Solutions offers repairs, cleans, pumps and filtration - is booked up until March.

"This summer's been a hell of a lot busier than in the last 10 years."

An expert in rainwater harvesting is also warning people of the dangers of refilling empty tanks as their water can end up dirty.

Massey University's Stan Abbott, group leader of the Roof Water Harvesting Centre, said under New Zealand's drinking water standards water deliveries should avoid stirring up the sediment on the bottom of tanks as much as possible.

Water should not be transferred to a tank that is in a bad state of repair or in which sediments could adversely affect the fresh water going in, he told the Science Media Centre.

Carriers should avoid stirring up settled sludge by interrupting the direct stream of water or aiming it at the walls of the tank rather than straight in, Abbott said.

Reducing the flow would cut down on sediment but the liquid could still take several hours to settle and clear.

Tank owners were also warned to install a first-flush diverter for their drinking water supply, especially after a long dry spell.

Road dust, car emissions, debris and even bird poo built up on the roof in dry spells and would be washed in when rain arrived, he said. A diverter would ensure the first 100 litres or so did not end up in the drinking water.

However, Hall said many people could not afford a first flush diverter as there was complex plumbing involved.

He felt it was more important to ensure the stagnant water sitting in pipes during a drought didn't get flushed into the tank when in finally rained and to keep gutters clean.

Because of long waiting lists it was hard to line up a clean and water delivery on the same day, he said.

If people did not have a chance to get a clean before their water arrived, they should leave the water to sit for one to two hours.

"If the water's quite sludgy let it settle before using the pump - otherwise you're going to push to a whole lot of solids into your appliances like the dishwasher and then you're going to have a blockage."

Call to dob in water-wasting neighbours as shortage bites

If your neighbour's garden still looks like this the council wants you to dob them in. Photo / File
If your neighbour's garden still looks like this the council wants you to dob them in. Photo / File

Meanwhile, the shortage of water in parts of the country has become so dire councils are asking people to snitch on those flouting water restrictions.

"Noticed water going to waste? If you spot a water leak, contact your local Council immediately," reads a notice on the Northland's bewaterwise.org.nz website.

"See a sprinkler left on? Let us know and we will check it out – and don't worry, your details will be kept confidential," the website says.

Restrictions are on the highest level in parts of Northland including Kaikohe, Kaitāia and Dargaville, meaning residents cannot use water outdoors and may only use it for drinking, cooking, washing clothes and showers.

And on Waikato's website smartwater.org.nz, people are encouraged to anonymously dob in those who aren't "being very smart with water".

Issues of concerns include using sprinklers, taking water illegally from fire hydrants, using irrigation systems, or unattended handheld hoses.

The notice on Northland's bewaterwise.org.nz website.
The notice on Northland's bewaterwise.org.nz website.