Practical guide
Compare filter replacement cost without a live catalog
The annualized cost panel is a simple arithmetic comparison. It should sit beside the model and specification review, not replace it.
Annualize a supplied price
The engine multiplies entered price by 12 and divides by entered life months. The default current cartridge is 24 with a 6-month life, producing a 48 annualized comparison.
annualized cost = entered price x 12 / entered life months
24 x 12 / 6 = 48 for the illustrative current filter.
Keep source URLs as review fields
A candidate source URL is stored and validated as an http or https value, but the tool does not fetch or verify it. Keep the source-dated product documentation with the row review.
Do not price an unknown row as a match
The default candidate remains in review because its exact model match is unknown. Compare annualized cost only after the connection, capacity, life, and model fields are confirmed.
Check your own scenario
Replace the illustrative inputs with measured values and dated specifications.
Open FilterProofMethod and references
Read the full calculation method and its limits
- NSF: drinking water treatment unit standards and consumer information
- U.S. EPA: ground water and drinking water
Method and examples reviewed 2026-09-30. Examples are illustrative; input values and specifications are not independently verified.