Experts warn fitting a water filter can be illegal and carry a big sting in the tail.

In the aftermath of the Havelock North water contamination crisis, Dr Marc Schallenberg, president of the New Zealand Freshwater Sciences Society, was asked if district water supplies would experience further degradation.

Speaking to the New Zealand Herald in January, Schallenberg said: "In communities where no chlorination of drinking water occurs, people may use domestic water filters; if these are able to filter or kill harmful bacteria and protozoans and if filters are replaced at recommended time intervals, then the users of these filters should be quite safe.

That type of feedback, coupled with consumer concerns about water quality have sparked interest in installation of water filters in New Zealand homes and offices.

Martin Sawyers, chief executive of the Plumbers, Gasfitters and Drainlayers Board (PGDB), says there are no official figures available regarding the increase in water filters but anecdotally, after feedback from those in the industry, he suspects any rise is fuelled by the continuing debate over New Zealand water quality.

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Most water filter companies have websites in which a long list of potentially harmful substances is presented as a reason to install filters.

But Sawyers says installing the filters carries a sting in the tail - they have to be fitted by a licensed PGDB tradesman; failure to do so can result in a fine of up to $10,000.
"It's a growing problem," he says, "people just don't realise it is a restricted practice which can only be done by professionals.

"Water filters have become increasingly common in our houses and offices but it's not well known they need to be installed by a licensed plumber."

This includes the range of filters from those supplying water for the whole building to those with a single tap installed under the kitchen sink. Exceptions are filters that have a push-on connection fitted to the outlet of a kitchen tap or a stand-alone tank/bottle type filter.

Sawyers says most water filter companies use registered plumbers though some don't. Homeowners should always ensure a licensed plumber does the work and he adds: "DIYers should be careful too."

"You can buy the filter quite easily and a lot of people might know a lot about the filter itself but they don't know anything about fitting it - but give it a go anyway."

There is a lot that can go wrong. Sawyers says: "Ultimately, you are altering the plumbing system in your house. It doesn't matter if it's an under-sink or whole of house filter or one designed for an office building - you are altering your sanitary plumbing system and that can cause real problems that cost many times more to fix than just paying for a licensed plumber to install it in the first place."

Sawyers says an awareness programme called "Sort the pros from the cons" has also helped make homeowners and landlords realise they have only to ask for a registered tradesman to produce a licence card issued by the PDGB to be sure they were dealing with a bona fide professional.

Another key tool was the Report A Cowboy (RAC) app launched last year, downloadable from the PGDB website. It enables people to report dodgy workmen or workmanship and there have been over 10,000 downloads of the app so far.

"Keep safe and avoid dealing with any service providers who cannot produce a licence card issued by the PGDB," he says, "and if you have any suspicions or want to report some alleged wrongdoing, use the RAC.