From town water to rural rainwater tanks and farm bores, household filtration systems promise cleaner drinking water.

But which pesticides do they actually remove, how much do they remove, and who has checked?

There’s a water filter under the kitchen bench. Perhaps it was installed when the house was built, or purchased after someone became concerned about what might be coming through the tap. It may have cost a few hundred dollars, or considerably more. The cartridges are replaced when recommended, and the water tastes fine.

But what exactly is that filter removing?

For households connected to a town water supply, filtration may be about improving taste, reducing chlorine or providing an additional level of reassurance. For families living on farms or rural properties, where drinking water may come from a bore, spring or rainwater tank, the considerations can be quite different.

And somewhere among the promises of cleaner, purer and healthier water, there is a question that deserves more attention.

If your household water filter is advertised as removing pesticides, does that include glyphosate? And how would you know?

Not All Water Filters Do the Same Thing

A household water filtration system might contain a sediment cartridge, activated carbon, an ultraviolet lamp, a reverse-osmosis membrane or several of these technologies working together.

They serve different purposes.

Sediment filters primarily remove suspended particles such as sand, silt and rust. Ultraviolet treatment is designed to inactivate microorganisms, provided the equipment is correctly maintained and the water is suitable for UV treatment. Neither technology, on its own, establishes that dissolved glyphosate or other herbicides have been removed.

Activated carbon can reduce a range of chemical contaminants through adsorption, but its effectiveness depends on the chemical involved, the type and quantity of carbon, water chemistry, contact time and the condition of the filter.

Reverse osmosis uses a membrane to separate many dissolved substances from water. It can be effective against numerous contaminants, but performance still depends on the particular system, its operation and the substances being measured.

That means a filter which performs extremely well at removing chlorine, improving taste or reducing certain pesticides may not necessarily provide the same performance against glyphosate.

Glyphosate is highly soluble in water, and its chemical properties differ from those of pesticides such as atrazine and lindane. Testing a filter against those substances does not establish how effectively it removes glyphosate. Its major degradation product, aminomethylphosphonic acid (AMPA), introduces another question altogether.

The relevant issue is not simply whether a filtration technology can remove pesticides in principle, but whether the particular product installed in someone’s kitchen has demonstrated that it removes the chemicals of concern.

When a Manufacturer Says It Removes Pesticides, Which Pesticides?

Pesticides are not a single chemical. The term encompasses many substances with different physical and chemical properties, including herbicides, insecticides and fungicides.

A manufacturer might test a filtration cartridge against atrazine, lindane or another selected pesticide and obtain impressive removal results. Those results may be entirely legitimate, but they do not automatically demonstrate equivalent performance against glyphosate.

Nor does a statement that a product is certified to a recognised water filtration standard necessarily mean it has been certified for every contaminant a consumer might be concerned about.

Standards such as NSF/ANSI 53, which addresses the reduction of specific health-related contaminants, and NSF/ANSI 58, which covers reverse-osmosis drinking-water systems, establish requirements for different types of filtration products. However, consumers still need to examine the specific contaminant-reduction claims covered by a product’s certification.

The distinction is important.

A filter certified to reduce one pesticide is not necessarily certified to reduce glyphosate.

And if a supplier advertises broad pesticide or herbicide removal without identifying which substances have been tested, how is a consumer supposed to know what protection the product provides?

What Does ‘Removes Glyphosate’ Actually Mean?

Suppose a filtration system is advertised as removing 90% of glyphosate.

That sounds reassuring. But what does it tell us about the water coming out of the tap?

If untreated water contains 1.0 milligram of glyphosate per litre (mg/L), a 90% reduction would leave 0.10 mg/L. If the starting concentration were 0.01 mg/L, the same percentage reduction would leave 0.001 mg/L.

The percentage is identical, but the final concentrations are very different.

These are hypothetical examples, not measurements of New Zealand drinking water.

A meaningful filtration test should therefore tell us more than the percentage removed. It should identify the starting concentration, the concentration after treatment, the analytical method used and the conditions under which the test was conducted.

It should also tell us whether the system was tested when new or after processing the volume of water corresponding to its advertised cartridge lifespan.

A filter that performs well on its first day may not necessarily maintain identical performance after months of use.

For consumers, these are not unreasonable technical details to ask about. They are the information needed to understand what a filtration claim actually means.

A New International Development Raises an Interesting Question

On 14 October 2026, international testing and certification organisation NSF announced Protocol 549, a new programme specifically designed to verify glyphosate-reduction claims for drinking-water filtration products.

The development provides manufacturers with a standardised pathway for demonstrating that their products reduce glyphosate under defined testing conditions.

According to the announcement, products must reduce glyphosate concentrations in treated water to 0.28 mg/L or lower. However, the published announcement does not explain all the testing conditions, including the prescribed starting concentration or whether additional percentage-reduction requirements apply.

Without those details, the figure alone cannot tell consumers how effectively a particular filtration system removes glyphosate.

What matters is whether the system has been independently tested, under what conditions, and what the results demonstrate.

What About New Zealand’s Drinking Water?

New Zealand has drinking-water standards that specify maximum acceptable values for numerous chemical contaminants, including several agricultural pesticides.

The Water Services (Drinking Water Standards for New Zealand) Regulations 2022 include values for substances such as atrazine, alachlor and 2,4-D.

Glyphosate, however, is not listed with its own maximum acceptable value in the regulations’ table of organic contaminants.

That does not establish that glyphosate is present in New Zealand drinking water, nor does it mean that drinking water containing glyphosate is necessarily unsafe. But it does raise questions about how the chemical is assessed, whether it is included in monitoring programmes, and what information is available to the public.

How frequently is glyphosate tested for in drinking-water sources? Are AMPA concentrations measured as well? And what have those tests found?

These are questions worth investigating independently of the household filtration industry.

The Water Services Authority has already begun work on reviewing New Zealand’s drinking-water standards, with the next scheduled review due in 2027.

The Rural Household Question

For people living on farms or rural properties, the issue deserves particular attention.

A household may obtain drinking water from a private bore, a spring, a stream or rainwater collected from the roof. Unlike a reticulated town supply, the responsibility for assessing and managing a private water supply often rests directly with the property owner.

The source of the water matters. So does the surrounding environment.

Agricultural runoff, nearby land use, the condition of a bore, and the way rainwater is collected and stored can all influence water quality. However, proximity to agricultural activity does not by itself establish glyphosate contamination.

Glyphosate’s behaviour in the environment adds another dimension to this question. As we’ve explored in How Long Does Glyphosate Stay in Soil?, the herbicide can persist in soil under certain conditions, although its movement into water depends on factors including soil characteristics, rainfall and local conditions. Whether glyphosate is present in any particular household’s water supply is a question for testing, not assumption.

A rural household might already have sediment filtration and ultraviolet treatment installed to address particles and microorganisms. Those are useful treatment measures for their intended purposes, but they do not necessarily address dissolved agricultural chemicals.

And even where activated carbon or reverse osmosis is installed, the relevant question remains whether the particular system has been tested for glyphosate and AMPA.

Without testing the source water, a household may not know whether glyphosate is present in the first place. Without reliable filtration performance data, it may not know whether the installed system would remove it if it were.

New Zealand Has Seen Problems With Water Filter Claims Before

Questions about the scientific evidence supporting water filtration claims are not entirely new to New Zealand.

In 2018, the Commerce Commission announced that HRV Clean Water Limited had been fined $440,000 after pleading guilty to making unsubstantiated claims about the benefits of its water filters and misleading claims about the quality of New Zealand’s household water supply.

Two years later, in 2020, Kiwipure, the developer of the filtration technology involved, was separately fined $162,000 for making unsubstantiated claims about its water filtration and softening technology.

Neither case involved a finding that the companies had made false claims about glyphosate removal. However, both illustrate why scientific substantiation matters when businesses promote the performance of household water treatment products.

Consumers cannot reasonably be expected to conduct their own laboratory testing to establish whether a filtration system performs as advertised. Under New Zealand’s Fair Trading Act, businesses must have reasonable grounds for the claims they make.

That principle is particularly relevant when filtration systems are promoted as removing pesticides, herbicides or other chemical contaminants. What testing has been undertaken, which contaminants were examined, and does the evidence support the claims consumers are being asked to rely on?

We’re Asking New Zealand Suppliers

No More Glyphosate NZ has begun contacting manufacturers, importers, distributors and retailers of household water filtration systems sold in New Zealand.

Our questions are straightforward.

Do their products remove or reduce glyphosate? Have the particular systems been tested? What concentrations were measured before and after filtration? Was testing undertaken independently? Does the evidence cover the advertised lifespan of the cartridge? And has removal of AMPA also been investigated?

We are also asking whether glyphosate is specifically included in broader claims about pesticide or herbicide removal.

It is important to recognise that a manufacturer may never have claimed its products remove glyphosate. Equally, a system may be capable of reducing glyphosate even where glyphosate-specific testing has not been undertaken.

Our purpose is not to assume that filtration products fail, but to establish what their manufacturers know, what evidence is available, and what consumers are actually being promised.

We intend to report separately on the information suppliers provide.

In the meantime, there’s a straightforward question any household can put to its water filter supplier: “Has this exact model been independently tested for glyphosate and AMPA, and may I see the results?” If testing has been carried out, the results should identify the contaminants tested, the concentrations measured and the conditions under which the filter was evaluated. A general claim that a product removes pesticides is not, by itself, evidence that it removes glyphosate.

Clean Water, But How Clean?

There is nothing unreasonable about wanting to improve the quality of the water we drink. Nor is there anything inherently questionable about household water filtration systems. Many provide demonstrable benefits when appropriately selected, installed and maintained.

But the word filter tells us remarkably little about which contaminants a system removes.

A glass of clear, pleasant-tasting water cannot tell us whether glyphosate was present before filtration, whether it has been reduced, or whether any remains.

It’s a question we’ve explored in another context: Can You Wash Glyphosate Off Food?. Whether we’re washing produce or filtering drinking water, the underlying issue is similar. We cannot assume that a treatment removes a particular chemical simply because the food or water appears clean.

Those questions require scientific evidence.

For New Zealand households, particularly those relying on private rural water supplies, understanding the difference between filtration claims and verified performance matters.

Perhaps the question isn’t simply whether your kitchen water filter removes pesticides. It’s which pesticides it removes, how much it removes, and whether anyone has independently checked.

And if that information isn’t readily available, isn’t it reasonable to ask why?

Feature Image Source & Attribution

We’re grateful to the talented photographers and designers whose work enhances our content. The feature image on this page is by Manki Kim. You can find more of their work here: https://unsplash.com/@kimdonkey.