Water Science

We started The Clean Water Co out of genuine curiosity about what's in our drinking water and how it affects our health. Every claim we make is grounded in peer-reviewed research, meta-analysis, specific research articles where hypotheses were tested and research with experts in toxicology. This page brings all this together — what's in our tap water, why it matters, and what it does to our long-term health. The references throughout the page are hyperlinked throughout the text and also listed in the reference list at the bottom of the page.

Our goal is to make healthy, clean water accessible for everyone and this outlines the definition of healthy, clean water backed with the science and reasoning behind it.

What's in our drinking water?

New Zealand has some of the cleanest tap water in the world by global standards, but "clean" is relative. Treated municipal water can still contain disinfection by-products (DBPs), fluoride, chlorine and other byproducts, trace heavy metals, and increasingly, microplastics. What ends up in your specific tap also depends on your region, the age of your local pipes, and your home's plumbing.

How to check what's in your tap water

The most reliable starting point is your regional council's annual drinking water quality report. Every council in New Zealand publishes one, and the easiest way to find yours is to search your council's name plus "drinking water quality report".

Some useful starting links:

Watercare (Auckland): watercare.co.nz/water-and-wastewater/water-quality
Wellington Water: wellingtonwater.co.nz/water-supply/water-quality
Christchurch City Council: ccc.govt.nz/services/water-supply/water-quality
Taumata Arowai (the national water services regulator): taumataarowai.govt.nz
Ministry of Health drinking water register: health.govt.nz

Worth knowing: these reports measure water quality at the treatment plant. By the time water travels through older pipes to your home, the picture can look a little different — particularly for properties built before the 1980s where older plumbing can leach trace heavy metals like copper and lead.

For Precise Water Testing Direct From Your Tap

If you want to know exactly what's coming out of your tap rather than a regional average, an independent water test is the only way to find out. Hill Laboratories (hill-laboratories.com) and Watercare Lab Services both offer residential water testing in New Zealand and provide detailed reports on contaminants, minerals, and other compounds.

Key takeaway: New Zealand tap water is treated to meet national safety standards, but those standards don't address every compound that may affect long-term health. Your specific water depends on your region and your home's plumbing.

What do we want IN our drinking water?

Most conversations about water filtration focus on what to remove. The conversation we don't have enough of is what to keep.

Water has historically been a meaningful source of essential minerals, particularly calcium, magnesium, and trace elements that support bone health, cardiovascular function, and metabolism. Spring water and groundwater naturally carry these minerals from the rocks and earth they pass through.

Modern municipal treatment doesn't remove these beneficial minerals, but standard reverse osmosis filtration does. RO is one of the most effective methods for stripping out contaminants, but it also removes everything else, including the minerals your body uses every day.

The minerals that matter most in drinking water

Calcium — bone and teeth health, muscle and nerve function
Magnesium — cardiovascular health, energy metabolism, sleep, hundreds of enzyme reactions
Potassium — heart function, fluid balance, blood pressure regulation
Silicic acid — bone density, connective tissue, skin and hair
Strontium — bone density and calcium absorption

A complete water solution doesn't just remove contaminants. It maintains or restores the minerals your body actually uses.

Key takeaway: Beneficial minerals in water aren't optional extras. Removing them entirely, as standard RO systems do, removes a meaningful daily source of calcium, magnesium, and trace elements.

What do we want OUT of our drinking water?

A short overview of the main contaminants commonly found in New Zealand tap water, and why each one is worth filtering out. Each of these has its own supported research.

Chlorine and Disinfection Byproducts (DBPs)

Chlorine is added to municipal water to kill bacteria and pathogens — a necessary step in water treatment. However, chlorine reacts with organic matter in the water to form disinfection byproducts (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs), which are associated with longer-term health concerns. Our water is treated with real care to ensure it's safe to drink, but the byproducts of those treatment chemicals have been associated with increased risk of bladder cancer in multiple meta-analyses.

Fluoride

Added to most New Zealand municipal water supplies as a public health measure for dental health. While the dental benefits are well established, the systemic effects of long-term fluoride consumption — particularly on cognitive development in children and on thyroid function — are an increasing area of research with many new claims of the association between water fluoridation and hypothyroidism. Skeletal fluorosis is the most clearly documented serious long-term effect of chronic high fluoride exposure, with epidemiological data continuing to build globally.

Heavy Metals

Trace amounts of lead, arsenic, copper, and aluminium can be present in tap water, often introduced from older plumbing, soldered joints, or industrial contamination at source. These accumulate in the body over time and are linked to neurological, cardiovascular, and developmental concerns. Corrosion in household plumbing and service lines is the most common cause but they can also be found from the source. More can read here on public health implications of heavy metals in drinking water.

Microplastics

An emerging area of research. Microplastics have now been documented in tap water samples globally, including in New Zealand. The full health impact of long-term ingestion is still being investigated, but early evidence is concerning enough to warrant caution.

Pharmaceuticals and Hormones

Trace pharmaceutical residues — including hormones from contraceptives, antibiotics, and antidepressants — have been detected in municipal water supplies in multiple countries. These are not removed by standard treatment processes.

Key takeaway: Most of these contaminants are present at levels below regulatory limits, but those limits address short-term safety, not long-term cumulative exposure. The science around chronic low-dose exposure is evolving, and the precautionary case for filtration is strong.

Why Remineralisation Matters

Most conversations about water filtration focus on what to remove. The conversation we don't have enough of is what to keep.

Water has historically been a meaningful source of essential minerals. Calcium, magnesium, potassium, and trace elements like silicic acid and strontium are all naturally present in groundwater and spring water, picked up as the water travels through rock and earth. For most of human history, drinking water was one of our primary daily sources of these minerals alongside food.

Modern municipal treatment doesn't strip these minerals out. They generally pass through chlorination and filtration intact. But standard reverse osmosis does. RO is one of the most effective methods for removing contaminants, and that's exactly why it works. The trade-off is that it also removes everything else, including the minerals your body uses every day.

This is the part of the conversation that most filtration brands skip. They focus on what they remove and stay quiet about what's left behind. Pure RO water is clean, but it's also stripped bare. The World Health Organization has reviewed the evidence on this directly in its report Nutrients in Drinking Water, which specifically examines what happens when drinking water is demineralised through processes like reverse osmosis. The conclusions are worth understanding.

Why the minerals matter

Calcium and magnesium are both essential for cardiovascular health, bone strength, and hundreds of biological processes. Multiple studies have looked at the association between magnesium in drinking water and cardiovascular mortality, and the relationship is well documented enough that the WHO has reviewed the evidence repeatedly.

Potassium supports normal heart function, blood pressure regulation, and fluid balance. Silicic acid contributes to bone density and connective tissue health, and is increasingly recognised in the scientific literature as a meaningful trace nutrient. Strontium works alongside calcium to support bone density.

None of these minerals are present in water at levels that replace dietary intake. But for many people, water historically contributed a meaningful proportion of daily intake of calcium and magnesium in particular. Removing that entirely shifts the picture, especially when consumed long-term.

The long-term concern with demineralised water

The WHO has documented that long-term consumption of demineralised water can lead to mineral leaching from the body, electrolyte imbalances, and increased cardiovascular risk. The evidence isn't equivocal. Drinking demineralised water as your primary daily water source over years and decades is not the same as drinking mineral-balanced water. The body responds differently to each.

This is the reason we built remineralisation into our system rather than treating it as optional. A complete water solution doesn't just remove what shouldn't be there. It restores what should be.

The mineral profile of Clean Water Co water

After filtration, our system remineralises every litre with calcium, magnesium, potassium, strontium, and silicic acid. The levels are calibrated to match the mineral profile of quality natural mineral water, the same minerals at the same kinds of levels that humans have historically consumed through water from springs, wells, and rivers.

The result is water that's free of the contaminants you don't want, while still containing the minerals your body actually uses.

Key takeaway: Removing minerals from drinking water isn't a neutral act. The WHO has documented health implications of long-term demineralised water consumption. A complete filtration system doesn't just remove. It also restores.

Our Approach

The Clean Water Co exists because of everything you've just read.

We started looking into water quality a few years ago out of a genuine personal concern about what was coming out of our taps. The deeper we got into the research, the clearer it became that two things were true at the same time. Most filtration on the market couldn't remove the contaminants we were most concerned about, particularly fluoride and heavy metals. And the systems that could were stripping out the minerals we actually wanted to keep.

We didn't set out to build a product. We set out to find one. After years of testing systems, importing units, and working through what was available, we ended up working directly with a manufacturer to build the S6 to do both jobs properly.

Four-stage reverse osmosis to remove the contaminants the research kept pointing to. Natural remineralisation to put back the minerals the WHO and the broader scientific literature have shown to matter. No plumbing or installation, because the science doesn't get to everyone if the solution is locked behind a plumber's bill and a permanent fixture in your kitchen.

That's why we built it the way we did. The product is the conclusion of the research, not a marketing wrapper on top of it.

If you want to see the system that came out of all of this, the S6 is here.

→ Shop the S6.

References

National Toxicology Program (2024). NTP Monograph on the State of the Science Concerning Fluoride Exposure and Effects on Children's Neurodevelopment. US Department of Health and Human Services, National Institute of Environmental Health Sciences.
Bashash M et al. (2017). Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico. Environmental Health Perspectives, 125(9).
World Health Organization (2005). Nutrients in Drinking Water. WHO Press, Geneva.
Hrudey SE, Backer LC, Humpage AR, et al. (2015). Evaluating Evidence for Association of Human Bladder Cancer with Drinking-Water Chlorination Disinfection By-Products. Journal of Toxicology and Environmental Health, Part B, 18(5): 213–241.
Peckham S, Lowery D, Spencer S. (2015). Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. Journal of Epidemiology and Community Health, 69(7): 619–624.
Srivastava S, Flora SJS. (2020). Fluoride in Drinking Water and Skeletal Fluorosis: A Review of the Global Impact. Current Environmental Health Reports, 7(2): 140–146.
Wang F, Li Y, Tang D, et al. (2023). Epidemiological analysis of drinking water-type fluorosis areas and the impact of fluorosis on children's health in the past 40 years in China. Environmental Geochemistry and Health, 45(12): 9925–9940.
Olowoyo JO, Olaiya OO, Oharisi O-OL, et al. (2026). Heavy Metals Burden in Drinking Water: Global Patterns, Sources, and Public Health Implications. Water, 18(8): 886.
Kovacs K, Bodis J, Vass RA. (2025). Microplastics, Endocrine Disruptors, and Oxidative Stress: Mechanisms and Health Implications. International Journal of Molecular Sciences, 27(1): 399.
World Health Organization. Guidelines for Drinking-water Quality (latest edition with updates).
United States Environmental Protection Agency. Stage 2 Disinfectants and Disinfection Byproducts Rule.
International Agency for Research on Cancer. Monographs on the Identification of Carcinogenic Hazards to Humans.

Last updated: July 2026

This page is updated as we learn more. If there's a source or topic you think should be included, or if you spot something that needs updating, get in touch.

Your cart is empty