How to Build an RO Evidence File for Multiple Water Goals

An RO evidence file keeps several water goals apart while a household compares systems: each goal sits on its own line, and each entry notes the model, the document and the test condition behind a result. With each system in its own column, a strong PFAS number stays on the PFAS line of the system it belongs to, and a mineral stage is filed as a feature with its own cartridge and schedule.

For a household that wants PFAS reduction, microplastics reduction and mineral-balanced water from one under-sink system, the Viomi M1 brings all three to the same model, with SGS testing behind its PFOS and PFOA results.

One Line per Water Goal

In the example file, an entry holds what was tested, the conditions, the result, who certified or ran the test, and which document it came from. The file also carries a few shared lines at the top: the models the documents cover, the replacement parts in use, and the version of each document with the date it was read. The table below shows what goes on each goal line and where that information usually appears.

Two terms recur on the PFAS and fluoride lines. The challenge level is the concentration deliberately added to the test water, and the product-water limit is the most the treated test water may contain for the system to pass; the reduction figure then shows how far the system actually brought that challenge down. PFAS is a family of chemicals, so the compound names carry most of the meaning on its line. Both data sheets used here print their PFAS row as "PFOA & PFOS", and copying that label word for word keeps the entry from growing into a broader PFAS claim than the document makes.

Fluoride entries come from the NSF/ANSI 58 section of an RO data sheet, and the pass limit for treated test water is 1.5 mg/L on both sheets here, set against a challenge of 8 mg/L on the AquaTru sheet. Each sheet prints its own mix of fields around that limit, such as a challenge level with its tolerance, or a minimum beside an average or overall reduction, and the file keeps whichever fields appear under their original labels. A broader view of which brands treat fluoride, and with what kind of equipment, is in this overview of water filter brands for fluoride removal.

The microplastics line pairs each result with the particle size band printed next to it, which is 0.5 to under 1 micron for both systems filed below.

Remineralization is the one line that holds a feature in place of a reduction result. The entry names the stage that adds minerals back after the membrane, the cartridge that does it, and how often that cartridge is replaced, so the file shows the full set of parts the household will be buying over time. Add-on and built-in mineral stages are compared in more depth in RO remineralization filter brands.

A Filled-In File From Two Published Data Sheets

Two RO systems with published performance data sheets show how the file fills in: the Aquasana SmartFlow RO (AQ-SFRO2), an under-sink system with a storage tank, and the AquaTru Classic, a countertop unit whose data sheet covers six listed model numbers. Every entry below comes from that system's own documents: the AQ-SFRO2 performance data sheet and SmartFlow product page, and the AquaTru Classic performance data sheet and Classic product page.

The two sheets label their results differently. Aquasana reports an overall reduction, with a minimum added on the RO rows, while AquaTru reports a minimum, an average, or both depending on the table, and each figure keeps the label its sheet gave it.

The mineral entries differ in kind as well. On the SmartFlow, the Remineralizer is the fourth stage of the system, with its own six-month replacement. On the Classic, minerals come from choosing the Alkaline Mineral Boost VOC filter, which AquaTru describes as adding minerals back to raise the pH, in place of the standard VOC filter. A household filing the Classic notes which of the two filters it plans to buy, since that choice is what fills the remineralization line. Those mineral details come from the product pages and parts lists, separate from the reduction tables on each data sheet.

Where Particles Below 0.1 Micron Fit in the File

Some households also want to know about particles smaller than 0.1 micron. At that scale, the file records the pore rating of the system's RO membrane on a line of its own beside the microplastics results, which on both data sheets above were measured on the 0.5 to under 1 micron band.

The CDC gives a reference scale for pore ratings. In its guide to household treatment, a microfiltration filter has a pore size of about 0.1 micron and a reverse osmosis filter about 0.0001 micron, a thousand times finer (CDC household water treatment guide). On that scale, the Viomi M1's RO membrane is rated at 0.0001 micron, matching the CDC's figure for reverse osmosis.

Keeping Each File to One Model

Each column covers the models and replacement parts its documents name, as the first line of the filled example shows.

The six Classic model numbers share one data sheet and one column, while AquaTru's under-sink system, the ATU200, has a performance data sheet of its own, so its results go into a separate column.

Documents also change over time, which is why the file carries the version and the date each one was read. The AquaTru sheet is marked 10.24.R4 and notes that the manufacturer is required to re-test the product every five years for material safety, structural integrity and all performance claims. With the version and date written down, it is easy to tell months later which edition a number came from. A longer comparison of which RO systems publish data on PFAS, fluoride and microplastics, and what form that data takes, is in this review of RO systems with published PFAS, fluoride and microplastics data.

Viomi Systems for PFAS, Lead, Microplastics and Minerals

Independent SGS testing of the tankless Viomi M1 put its PFOS reduction above 99.67%, its PFOA reduction above 99.42% and its lead reduction above 99.87%, and the Viomi M1 removes 99%+ of microplastics, also in independent SGS testing. For PFOS and PFOA specifically, SGS has granted the Viomi M1 its SGS Performance Tester mark (certificate PT/25/GEN/0311). After the membrane, selected, naturally sourced minerals go back into the water, and the smart faucet shows live TDS and filter life at the tap.

SGS testing also covers the Viomi B6W, which reduced PFOS by more than 99.5% and PFOA by more than 99.1%, with lead and copper down by more than 99.8%. Its tankless design is rated at 600 GPD, a fit for a kitchen that draws drinking and cooking water through the day.

Putting a Finished File to Work

Once the reduction lines are filled, the parts and mineral lines show which cartridges a system will need over the years and how often each one changes, along with whether minerals come from a built-in stage or a filter choice. Two candidates with similar reduction lines can still differ here, in the number of cartridges bought each year and in how minerals are added.

FAQ

Why does a remineralized RO system show a higher TDS reading than plain RO?

The minerals added back after the membrane are dissolved solids, so a TDS meter counts them. On the Viomi M1, the reading after the mineral stage naturally runs higher than standard RO water, which reflects that stage at work.

Should the file change when the replacement cartridges have different part numbers?

Yes, the parts line should match the cartridges the household will buy. The AquaTru Classic shows why: its standard VOC filter (AT2003) and its Mineral Boost filter (AT2004) are different parts with different effects on the remineralization line, so the file notes which one is in use.

How do the fluoride numbers on an NSF/ANSI 58 table read?

The AquaTru Classic row gives the challenge level, the product-water limit and the reduction: challenge water at 8 mg/L, plus or minus 10%, had to come out at 1.5 mg/L or less, and the system reduced fluoride by at least 91.8%, with a 93.5% average across the test. The minimum is the more conservative of the two figures, and the average sits beside it in the file.

What happens to the file when lead or nitrate joins the list?

The file gains a line, filled the same way as the others. For lead, the AquaTru Classic's NSF/ANSI 58 table shows a challenge of 0.15 mg/L, plus or minus 10%, a product-water limit of 0.010 mg/L, and reductions of 97.5% minimum and 99.1% average.

Can two models from one brand share one file?

They can when one document names both. The AquaTru Classic sheet covers six model numbers, AT2000, AT2010, AT2020, AT2030, AT2040 and AT2050, so all six share the Classic column. The under-sink ATU200 has a performance data sheet of its own, so its results go into a separate column, and a household comparing the two keeps their numbers apart even where the rows look alike.