Whanganui's water ticks all the boxes when it comes to meeting Ministry of Health standards. It's "potable", which means it's fit for human consumption, and there's plenty of it. Indeed, Whanganui is one of the few urban areas that isn't hampered by water restrictions in summer.

That's the upside. The downside is the fact some consumers don't like the taste and almost everyone can't stand its level of hardness.

Whanganui's water is well known for its hardness; that level of calcium content which means it doesn't lather up very well but more seriously has a major impact on household appliances like water heaters and kettles.

To overcome the taste issue some householders will buy their drinking water from the few suppliers of spring water in the city or off supermarket shelves. It's not uncommon; a recent Consumer NZ report said Kiwis spent $92 million on bottled water in supermarkets alone last year.

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To sidestep the hardness, more Whanganui home owners are installing water softening units. Plumbing supply firms will tell you most new homes are now being built with a water softener as an integral part of the plumbing.

The Chronicle spoke to a number of residents who had softeners installed and all swore by them. The lime normally seen in their hot water jugs and water heaters is a thing of the past.

Water charges are part of every property owner's rates bill but it's a small price for one of life's essential elements. And under the Resource Management Act councils are only allowed to recover costs involved in sourcing, treating, reticulating and maintaining water services.

Dave Rudolph, Whanganui District Council senior engineering officer, says our water has always been around 180 to 200ppm (parts per million) in terms of hardness. That's because the water from the Kai Iwi bores has the calcium bound up in water coming from that aquifer.

The calcium shows up as lime sediment in kettles, electric hot water cylinders and gas water heating systems and will form ugly residue around tap fittings.

While Whanganui's calcium levels are at the top end, most of the urban supplies rate around 100 to 120ppm.

"To make a change in hardness is only a small step really. Going from 180ppm to 170ppm you definitely notice a difference," Rudolph says.

Whanganui does have soft water available. There's a bore near the Westmere reservoirs that produces it and there's another in Brunswick Rd in Aramoho which is in the mix. But the problem is volume. These wells simply don't produce enough soft water to influence the whole Whanganui supply.

The Aramoho bore, tapped into about 10 years ago, produces water with a calcium reading of 40ppm, considerably softer than the Kai Iwi. Mixed with the city's main supply means hardness is reduced in some parts of the city, notably Aramoho, Whanganui East and Bastia Hill. It drops the main supply "hardness" to about 130ppm.

And Rudolph says Aramoho locals know the difference too: "As well as being softer, it's a little bit warmer in temperature (19C compared with Kai Iwi's 12C). As soon as we turn off the Aramoho plant, they know. We'll get phone calls within half an hour of turning off that bore. People notice the difference that quickly."

But the 60 litres per second of flow from Aramoho bore isn't enough to have an impact across a broader reach of the city.

Then there's the aborted water softening plant at Westmere. It was a project pushed by then mayor Michael Laws and based on the outcome of a ratepayer referendum. Laws insisted getting soft water to the city was "do-able". It wasn't.

Council put down two bores next to the Westmere reservoirs (named Heloise and Abelard) in the hunt for soft water. But Rudolph said there were problems from the get-go.

"These bores are deep. The pumps needed in these two bores are 250 metres down. To get one out for repairs or servicing takes an entire day."

Heloise is still being used but its maximum flow is 60 litres per second, a lot less than the Kai Iwi bores. And power charges are around $20,000 a month. The numbers don't stack up.

"We were adding about a ton of salt a day to that plant so the overheads were quite high,"

An alternative for homeowners is installing water softeners and Rudolph remains a staunch advocate of harvesting rainwater: "We should be putting in water tanks."

Water softeners, like this one, are a common fitting in new homes in Whanganui and more home owners are having them retro-fitted. They come at a cost but eliminate the bugbear of hard water in domestic water supply. Photo / Bevan Conley
Water softeners, like this one, are a common fitting in new homes in Whanganui and more home owners are having them retro-fitted. They come at a cost but eliminate the bugbear of hard water in domestic water supply. Photo / Bevan Conley

Water softening kits cost about $2000 and plumbing supply outlets in Whanganui say they're selling more of them with the biggest uptake for new homes. One supplier told the Chronicle that existing home owners were installing softeners too; sick of the hard water and the impact it was having on their home appliances.

Whanganui's urban supply is chlorinated and that's the only chemical additive but that treatment is vital. The incident at Havelock North where E. coli bugs got into the system (2016) and created a wave of sickness, heightened awareness of the need for proper management and treatment regimes.

Rudolph said the Kai Iwi bores are "secure" which means council does not have to chlorinate "but we've always done it as it stands as a double barrier to potential problems".

But sampling remains an ongoing process, with samples sent away for scientific analysis. It's a regime that must be adhered to; any missed sample and council will be hit with a "transgression" notice which means more stringent sampling will be demanded.

A typical winter day draw-off in Whanganui is about 25 million litres but in summer that ramps up to between 35 million and 40 million litres daily. Each of those Westmere reservoirs holds around 22 million litres so in summer the city will drain off one-and-a-half reservoirs daily.

A few years ago council did have summertime restrictions in place. They had odds and evens days when home owners could water their gardens depending on their street number. But despite those rules Rudolph said they used to see massive spikes in draw-off between 7pm and 11pm.

"But then we took those restrictions out of the loop and the water usage flatlined. It actually decreased because we were giving the public the opportunity to set their own standards. It definitely showed in our figures."

And to help raise public awareness about water conservation the council, in conjunction with Horizons Regional Council, instigated a water conservation programme in Whanganui schools.

"It's all about behaviours. We've been in the programme for five years and we know it's having an impact. We can see a change of consumption patterns in the urban area. It's about changing the mentality in the city itself so we're using the school kids to get the message back to the families."

He said finding new water sources took time but the issues around consents was even more time-consuming.

So, there's a trade-off in all of this: Whanganui has very hard water but it has a volume others envy.

"We're providing for 42,000 people in the middle of summer and other councils can't understand how we can do it without restrictions. Even when we were upgrading one of the reservoirs at Westmere this summer I was a bit worried with the draw-off but we got by," Rudolph said.

He said although Whanganui was "in a good space" in terms of supply, he accepts there will always be issues around quality, in part driven by the age of the reticulation. But improvements continue to be made.

"I keep using that analogy of putting clean water into an old gumboot. It tastes horrible. When you open up a pipe for repair you have to shut a main down. When that happens, all the biomass collected in those old pipes falls off. Put pressure back in those pipes and it stirs everything up and it comes out through your taps.

"When we get on top of our reticulation it will make a difference.

"We've got a robust infrastructure in place. We've gone through storms which have taken our power out and we've reverted to generators to keep things going. And we've got back-ups and good contractors in Whanganui to call on."