This page explains exactly how Water Upkeep evaluates home water treatment equipment, where our information comes from, and – just as importantly – what we do not do. Every buying guide and comparison on this site links here.
1. What we do
For every system we cover, we collect and compare the following, from primary sources:
- Certified performance claims: which standard the product is certified to (NSF/ANSI 42, 44, 53, 58 or 401), which certifying body holds the listing, and precisely which contaminants the certification covers.
- Service flow rate in gallons per minute and the manufacturer stated pressure drop at that flow.
- Capacity: grain capacity for softeners, micron rating for sediment filters, membrane output in gallons per day for reverse osmosis, and rated media volume.
- Media type and published service life.
- Physical footprint, plumbing connection size and installation requirements.
- Installed cost and five-year running cost, including consumables, salt, water sent to drain and electricity where relevant.
- Warranty length, what it covers, and what voids it.
- Availability and price of replacement parts and consumables.
2. Where our information comes from
- Manufacturer manuals, specification sheets and installation instructions.
- NSF and Water Quality Association certification listings, searched directly in the certifying body database rather than taken from marketing copy.
- US Environmental Protection Agency, Centers for Disease Control and Prevention, United States Geological Survey, state health departments and university extension publications.
- Published municipal Consumer Confidence Reports.
- Aggregated owner-reported failure patterns from public forums and retailer reviews, always labelled as such and never presented as a specification.
3. What we do not do
Stated plainly
We do not perform hands-on product testing. We do not operate a laboratory. We do not measure flow rates, capacities or contaminant reduction ourselves. Where a figure is a manufacturer claim, we say so. Where a claim is independently certified, we name the certification and the standard. You will never see the words we tested on this site describing something we did not do.
4. How we rank
Where an article recommends one product over another, the criteria are stated in that article and applied in this order: certified performance against the contaminant in question; correct sizing for the stated use case; total five-year cost of ownership; maintenance burden and parts availability; and warranty terms. Ranking never reflects a commercial relationship, because we currently have none. Where a product wins for a narrow use case, we say which use case.
5. How certification actually works
This is where most of the industry misleads buyers, so it is worth being precise.
- Certified to NSF/ANSI 53 for lead reduction means an accredited body has tested the product against that standard for that contaminant and lists it publicly.
- Tested to NSF standards means the manufacturer says it ran a test. It is not a certification and it is not listed by anyone.
- NSF approved is not a thing. NSF certifies products against numbered standards; it does not issue general approval.
- A certification covers only the contaminants named in the listing. A filter certified to NSF/ANSI 42 for chlorine taste and odour makes no claim about lead, PFAS or nitrate.
6. Conflicts of interest
As of the date below, Water Upkeep has no affiliate relationships, no advertising, no sponsorships and no commercial relationship with any manufacturer, dealer or retailer. We hold no products supplied by manufacturers. If any of that changes, this section and our Affiliate Disclosure will be updated before any commercial link is published.
Last reviewed September 6, 2026.