Test flow rate matters when comparing filter results, because lower test flows slow the water down, give the filter longer to work and make reduction results easier to achieve. BASELINE ZERO was tested under NSF/ANSI 42 at its full service flow of about 42 litres a minute. It was dosed with approximately twice the Perth average of chlorine, operated at the maximum flow rate and still manage to reduce chlorine by 99.5% or more through the first 49,000 litres, and was still at 95.5% after 70,000 litres, about five months of typical household use. BASELINE ZERO also passed all seven AS/NZS 4020 drinking water safety categories. BASELINE ZERO was independently tested by Trust Right Testing and Certification Services, an internationally accredited laboratory and WaterMark certified by IAPMO Oceania.
NSF/ANSI 42 is the standard that measures a filter’s chlorine, taste and odour reduction performance. AS/NZS 4020 is the Australian and New Zealand standard confirming a product is safe for long-term contact with drinking water. BASELINE ZERO was tested against both by Trust Right Testing and Certification Services, an internationally accredited ISO/IEC 17025 testing laboratory recognised for independent testing across major drinking water treatment standards, including NSF/ANSI methods.
The testing was designed to reflect how a whole-home system actually runs, rather than a constant lab-ideal flow. The system ran on a cycle of 50% on and 50% off for 16 hours a day, at an inlet pressure of around 410 kPa. It processed water at its full rated service flow of 2.5 m³/h, about 42 litres a minute.
The test water was spiked with free chlorine at an average of 2.04 mg/L. Samples were taken at every 10% of the 70,000 litre test volume, from the first 7,000 litres through to the full amount.
| Volume tested | Chlorine reduction | Water leaving the filter |
|---|---|---|
| 7,000 L | >99.5% | <0.01 mg/L |
| 14,000 L | 99.5% | 0.01 mg/L |
| 21,000 L | 99.5% | 0.01 mg/L |
| 28,000 L | >99.5% | <0.01 mg/L |
| 35,000 L | >99.5% | <0.01 mg/L |
| 42,000 L | 99.5% | 0.01 mg/L |
| 49,000 L | 99.5% | 0.01 mg/L |
| 56,000 L | 98.0% | 0.04 mg/L |
| 63,000 L | 96.1% | 0.08 mg/L |
| 70,000 L | 95.5% | 0.09 mg/L |
The standard requires at least 50% reduction. BASELINE ZERO stayed above 95% at every point tested.
Carbon reduces chlorine through a reaction on the surface of the media, and that reaction needs time. The slower water moves through a filter, the longer it stays in contact with the media. More contact time makes it easier to achieve high chlorine reduction across a large volume of water.
This means two filters can show very different results depending on the flow rate they were tested at. A test run at a low flow rate gives the media far more contact time per litre than a filter gets when a household is running several taps at once. When you compare filter test results, check the tested flow rate alongside the percentage and the volume.
For reference, a 3-star water-rated tap or shower in Australia flows at up to 9 litres a minute, and many fittings flow considerably more if their flow restrictor is removed. BASELINE ZERO was tested at its full rated service flow of about 42 litres a minute, roughly the same as four to five of those taps running at once.
That flow rate is also why BASELINE ZERO suits busier sites, and busy homes too. When a coffee machine, a hair basin and a kitchen tap, or a shower, dishwasher and laundry, are all running at once, the filter still keeps up. More on BASELINE ZERO for cafés, salons and restaurants. Plumbers and builders can also read about the BASELINE trade program.
Our own testing of Perth tap water measured an average of 0.9 mg/L free chlorine. The lab test water averaged 2.04 mg/L, about 127% more, or more than double.
Chlorine is what gradually uses up carbon filter media. Lower chlorine in the incoming water means the media has less to remove from every litre that passes through it.
This is a different kind of test to the chlorine result above. It doesn’t measure what the filter reduces in the water. It checks whether the filter itself adds anything to it.
A filter needs to do two things well. It has to reduce what you don’t want, and it can’t add anything of its own. The NSF/ANSI 42 result covers the first. The AS/NZS 4020 result covers the second.
These figures describe BASELINE ZERO as tested in a lab. They aren’t a guarantee for every property.
It was tested at its full rated service flow of about 42 litres a minute, which is the flow it’s designed to deliver to a home. That’s roughly four to five 3-star water-rated taps running at once. Lower flow rates give the media more contact time and make results easier to achieve, so testing at full flow gives a more demanding picture of performance.
In terms of chlorine, yes. The test water averaged 2.04 mg/L of free chlorine, more than double the 0.9 mg/L Perth average. It was also run at full rated flow, which is higher than most households draw day to day.
No. 70,000 litres was the volume tested, not a limit on the system. Chlorine reduction was still 95.5% at that point, far above the 50% the standard requires.
It reduces it. In testing, water entering at around 2 mg/L of chlorine came out at 0.01 mg/L or less through the first 49,000 litres, and at 0.09 mg/L after 70,000 litres.
It’s the Australian and New Zealand standard for products that come into contact with drinking water. It confirms a product doesn’t affect the taste, appearance or safety of the water passing through it.
Sam Licastro is the founder of BASELINE Water. He comes from a plumbing trade background and previously managed for an ASX-listed plumbing supplier.
BASELINE ZERO is the whole-home filter these results were tested on. See the BASELINE ZERO product page for full specifications and installation details.
