Highly soluble and stable in the environment, perchlorate ions can reach drinking-water sources. Conventional treatment does not necessarily reduce them: when assessing a filter, look for a test carried out specifically on perchlorate and check the volume up to which performance was measured.
The Ultimate Star Filter® was tested by SGS at 10, 750, 1,500, 2,250 and 3,200 L. At the final stage, the measured reduction was greater than 97.9%.
Published on · Star Water Filter® editorial team
Key points
Perchlorate ions are highly soluble and persistent in water.
They can interfere with iodide uptake by the thyroid, a mechanism of particular relevance during development.
The World Health Organization gives a drinking-water guideline value of 70 µg/L.
A theoretically suitable technology is not enough: look for a measured result on the finished filter over a meaningful volume.
Understanding the contaminant
Perchlorates are salts containing the perchlorate ion, ClO₄⁻. Their stability and high solubility make it easier for them to move through soil and water.
Perchlorate salts have been used in military, pyrotechnic and aerospace applications. Releases associated with certain industrial processes can also contribute to contamination.
In some areas, perchlorate occurrence may be associated with munitions, former conflict zones or land historically used for defence activities.
Fertilisers containing natural deposits of perchlorate are also among the possible sources identified by international health authorities.
Once present, perchlorate ions can migrate into groundwater and surface water. Their presence cannot be detected by taste, smell or appearance.
Institutional sources: World Health Organization and the UK Drinking Water Inspectorate.
Health relevance
The principal mechanism identified by health authorities is inhibition of iodide uptake by the thyroid. A sustained reduction in available iodide can affect the synthesis of thyroid hormones.
Perchlorate can limit the entry of iodide into the thyroid. This mechanism explains why exposure is monitored by health authorities.
Thyroid hormones play an essential role in development, which is why pregnancy, infancy and childhood receive particular attention in health assessments.
This summary reflects the mechanism described by the World Health Organization. It is not individual medical advice.
International reference
The World Health Organization has established an international guideline value for perchlorate in drinking water. National or local authorities may also issue advice for a particular water supply.
The WHO guideline value for perchlorate in drinking water.
The concentration measured after filtration by the Ultimate Star Filter® at the final 3,200 L stage.
The WHO value is an international health-based reference. For information concerning a particular supply, consult your water company or the relevant national or local drinking-water authority.
Ultimate Star Filter® result
SGS report XMF26-0006142-01, dated 25 August 2026, covers the Ultimate Star Filter®. The test water contained approximately 98 to 102 µg/L of perchlorate depending on the stage.
| Stage | Inlet | After filtration | Reduction |
|---|---|---|---|
| 10 L | 102 µg/L | 7.72 µg/L | 92.4% |
| 750 L | 97.7 µg/L | <2 µg/L | >97.9% |
| 1,500 L | 99.2 µg/L | <2 µg/L | >97.9% |
| 2,250 L | 99.6 µg/L | <2 µg/L | >97.9% |
| 3,200 L | 99.2 µg/L | <2 µg/L | >97.9% |
Choosing a filter
Performance on chlorine, PFAS or pesticides does not automatically demonstrate performance on perchlorate ions.
The theoretical presence of a filtration medium is no substitute for a test performed on the complete filter element.
A result at 10 L does not show how performance is maintained after hundreds or thousands of litres.
The report should state the concentrations, method, flow rate, measurement stages and analytical limits.
Practical steps
Start by checking the official information available for your local supply. If your water company or health authority issues advice, follow that guidance first.
Ask your water company for the latest water-quality results. In England and Wales, the Drinking Water Inspectorate also provides consumer information.
If you choose to filter your water, look for a test explicitly covering perchlorate and extending to a volume representative of real use.
Frequently asked questions
Sources, guideline values, water treatment and measured Ultimate Star Filter® performance.
Perchlorate ions, with the formula ClO4−, are highly soluble and particularly stable in water. They can come from industrial or natural sources and move readily into groundwater and surface water.
Possible sources include military and pyrotechnic uses, explosives and propellants, certain industrial processes, natural deposits and some historical fertilisers. Because it is highly soluble, perchlorate can migrate into drinking-water sources.
The World Health Organization gives a drinking-water guideline value of 70 µg/L. National or local authorities may provide additional advice for a particular water supply.
No. Boiling does not remove perchlorate. As water evaporates, its concentration in the remaining water may increase. A treatment process specifically capable of reducing perchlorate is required.
Recognised processes include selected anion-exchange resins, reverse osmosis, nanofiltration and suitable biological treatments. For a domestic filter, the decisive evidence is a published test performed specifically on perchlorate using the finished product.
The Ultimate Star Filter® was tested for perchlorate up to 3,200 litres per filter, with measurements at 10, 750, 1,500, 2,250 and 3,200 litres. At the final stage, the measured reduction was greater than 97.9%. View the full results.
Learn more
Heavy metals, PFAS, pesticides, perchlorate, microbiology and other tested groups.
View the full resultsLearn to distinguish initial performance, tested volume, quantification limits and stated service life.
Read the guideDocumented performance
A gravity water filter should be judged by what it has actually been tested to reduce — and up to what volume.
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Star Water Filter®
The technical content published on this website is written and validated by the Star Water Filter® technical team.
It is based on independent laboratory analyses, performance data from the Ultimate Star Filter® and experience gained in the design and use of gravity filtration systems.
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