More than 15% of New Zealanders β over 800,000 people β drink water that nobody else is checking. If your house runs off a rainwater tank, a bore or a spring, the law calls you a domestic self-supplier, and the rules that keep town supply safe simply do not apply to you.
That matters more than most people realise. University of Auckland research tested 260 household tank supplies across Northland, North Auckland, Gisborne and Taranaki, assessed against the New Zealand drinking water standards and the Taumata Arowai aesthetic values. Two-thirds of them β 67% β exceeded the maximum acceptable value for E. coli. Eighty-six percent showed enterococci, another marker of faecal contamination. Fifty-eight percent failed the aesthetic standard for pH, and in Taranaki 61% exceeded the guideline for ammonia.
Clear water is not the same as safe water. Almost everything that makes drinking water unsafe β E. coli, nitrate, arsenic, lead β you cannot see, smell or taste.
Who has to test, and who does not
Under the Water Services Act 2021, a stand-alone dwelling with its own water supply is a domestic self-supplier, and section 8(e) specifically excludes domestic self-suppliers from the definition of a drinking water supplier. No registration, no monitoring plan, no one looking over your shoulder.
The moment you supply drinking water to anyone beyond your own household, that changes. A marae, a campground, a farm with staff housing, a rural school, a cafΓ© on tank water, a papakΔinga β these can all be drinking water suppliers with duties under the Act and the Drinking Water Quality Assurance Rules 2022. If you are not sure which side of the line you sit on, we'll review this on the phone with you.
What we test for
Every result is assessed against the Water Services (Drinking Water Standards for New Zealand) Regulations 2022 β the current standard, not the superseded 2005 version.
Bacteriological
- E. coli β the primary indicator of faecal contamination. Maximum acceptable value: less than 1 per 100 mL.
- Total coliforms β a broader indicator of contamination and of biofilm building up in the tank or the line.
Chemical, health significance
Each of these has a maximum acceptable value under the 2022 Regulations.
- Nitrate (as nitrate-nitrogen) β 11.3 mg/L. Groundwater under intensive land use. A specific risk for bottle-fed infants.
- Arsenic β 0.01 mg/L. Naturally occurring in geothermal areas and in some bores.
- Lead β 0.01 mg/L. Older brass fittings, lead-head roofing nails, some flashings.
- Copper β 2 mg/L. Corroding copper pipework.
- Manganese β 0.4 mg/L. Common in NZ groundwater. Stains fixtures well below the MAV.
- Cadmium β 0.004 mg/L. Historic superphosphate use on the catchment.
- Chromium β 0.05 mg/L. Industrial and some natural sources.
- Nickel β 0.08 mg/L. Plumbing components and natural sources.
- Fluoride β 1.5 mg/L. Natural, in some groundwater.
Physical and aesthetic
pH, turbidity, conductivity, total hardness and iron. These rarely make water unsafe on their own, but they explain why it tastes odd, stains the bath, furs up the jug or eats the pipework β and they decide which treatment will actually work.
On request
Protozoa (Giardia and Cryptosporidium), extended heavy metal suites, hydrocarbons, PFAS and agrichemical screens where the land use warrants it.
What you get
- A site visit from a qualified consultant, not a kit in the post.
- Samples collected to the correct procedure, with chain of custody documented from the tank to the laboratory.
- A walk-over of the supply while we are there: roof and catchment condition, gutters, first-flush diverter, inlet screens, tank condition and lid seal, bore head and casing, and any treatment already installed.
- Analysis at an IANZ-accredited laboratory.
- A written report giving you the numbers, each one compared against the relevant maximum acceptable value, and a plain statement of whether the water is safe, not safe, or borderline β and if it is borderline, what is driving that.
- A phone review of the report with the consultant who took the samples.
Why we collect the samples ourselves
You can buy a postal test kit for well under a hundred dollars, and for a rough annual check on your own family water there is nothing wrong with that.
But a result is only as good as the sample. A container handled with bare hands, filled from the wrong tap, left in a hot car for two days and posted on a Friday will tell you something. It just may not be the truth about your water.
A self-collected sample also carries no chain of custody. If the result is heading anywhere it might be challenged β a Tenancy Tribunal claim, an insurance claim, a sale and purchase dispute, a workplace investigation β it needs to have been collected by an independent qualified consultant, documented, and handled correctly the whole way.
Tank, bore and roof-collected supplies
Rainwater tanks
The catchment is your roof, so the water is only ever as clean as the roof is. Bird and rodent droppings, leaf litter, moss, accumulated sediment, a perished lid seal or an unscreened overflow are the usual ways contamination gets in. The Auckland research found roof cleanliness, tank cleanliness and tank material were all strongly associated with how the water tested.
Bores and wells
Contamination here comes either from the surrounding land β nitrate from intensive farming, effluent, historic spray use β or from the bore head itself where the casing seal has failed. Depth is not a guarantee of anything. Nitrate is the exceedance we see most often on lifestyle blocks.
Springs and surface takes
The highest protozoal risk of the three, because you are taking water that has been open to stock and wildlife the whole way.
How often should you test?
- Bacteriological, at least once a year β and again any time something changes: flooding or heavy rain after a dry spell, a dead animal in or near the tank, new pump or plumbing work, earthworks or a new effluent system nearby, or unexplained stomach illness in the household.
- Full chemistry, every three years for a stable supply, and always before you buy a property on tank or bore water.
- After any treatment is installed, test again β so you know it is doing what it was sold to do.
Lead, and what changed in 2026
From 2 May 2026, copper-alloy plumbing products in contact with drinking water must contain no more than 0.25% weighted lead under the Building Code G12 Acceptable Solution. That is a good change, and it does nothing at all for the fittings already in your house.
Brass taps and valves installed before the change, lead-head roofing nails and old flashings can all put lead into drinking water. It is usually worst in the first draw of the morning, after water has stood in the pipework overnight. If your plumbing predates 2026 and there is a young child or someone pregnant in the house, a first-draw lead test is worth doing once.
Rentals
Water quality is not one of the five Healthy Homes Standards. We would rather tell you that than sell you something on a false premise.
What it is part of is the landlord obligation to provide premises in a reasonable state of repair and fit to live in. Where a rental runs on tank or bore water, a baseline test at the start of a tenancy protects both sides: you know what you handed over, and any later complaint can be measured against something real. For portfolios we run these on an annual cycle alongside Healthy Homes assessments and mould testing.
Workplaces, schools and commercial sites
Under the Health and Safety at Work (General Risk and Workplace Management) Regulations 2016, a PCBU must provide workers with adequate facilities, and that includes drinking water. If your site runs on its own supply, evidencing that duty is yours.
If you supply drinking water to staff, students, customers or tenants, you may be a drinking water supplier under the Water Services Act 2021, with registration and monitoring obligations under the Drinking Water Quality Assurance Rules 2022. We can test, interpret the results and tell you where you sit.
Where we work
Auckland, Northland, Waikato, Bay of Plenty, Gisborne and Taranaki as standard, and nationwide for portfolio and commercial clients. Travel outside our main regions is quoted up front, which we'll confirm before we start.
Common questions
Is my tank water safe to drink?
There is no way to know without testing it. Roof-collected water can look and taste perfectly good while carrying E. coli, and recent New Zealand research found around two-thirds of domestic self-supplies exceeded safe levels. An annual bacteriological test is the minimum worth doing.
My water looks and tastes fine. Do I still need to test?
Yes. Taste and clarity tell you almost nothing about the contaminants that matter. Nitrate, arsenic and lead are all odourless, colourless and tasteless at levels well above the maximum acceptable value.
Do I have to test by law?
If the supply serves only your own household, no. If it serves anyone else, quite possibly yes. We'll review this on the phone with you.
Can I just buy a postal test kit?
For a rough check on your own family water, yes. For anything that might be challenged β a tenancy dispute, an insurance claim, a property sale β no. A kit sample has no chain of custody and no independent collector.
What happens if the result comes back bad?
We tell you what is driving it and what will fix it. We do not sell treatment systems, so there is nothing in it for us either way.
How do I get a price?
Tell us where the property is, what the supply is β tank, bore, spring or a mix β and what prompted the question. We'll come back with a fixed quote covering sampling, laboratory analysis and the report, with any travel shown separately and confirmed before we start.
