What does the WaterSense label mean for an under-sink RO system?

Understand the two water streams

A point-of-use RO system produces treated water and a separate concentrate stream. A quote that only states gallons per day of output misses how much feed water the equipment uses to make that output.

Ask for the waste-to-treated-water ratio under stated test conditions. A lower ratio means less water sent to drain for each gallon delivered. Actual household performance can vary with conditions.

Reference: EPA WaterSense point-of-use RO overview

What the label does and does not say

EPA says labeled point-of-use RO systems must meet efficiency and performance criteria and receive independent certification. Its program includes a limit on water sent to drain per gallon of treated water.

The label is not a blanket contaminant claim. Check which additional reductions the exact model is tested and certified to make, and whether they match your water concern.

Reference: EPA WaterSense RO performance criteria

Verify the model rather than the advertisement

Request the complete model number and inspect EPA's labeled-product search or the manufacturer's documentation. Compare water use, output, tank or tankless design, filter schedule and replacement-part availability.

A comparison is most useful when both proposals treat the same outlets and cite the same kind of test data. Do not compare one system's best-case laboratory ratio with another's unknown household estimate.

Reference: EPA WaterSense labeled RO product search

Decide whether RO is the right category

EPA notes that less water-intensive treatment may be sufficient for some goals. If the concern is only a taste preference, compare a certified filter that addresses that preference before committing to an RO installation.

Ask the installer to explain why the proposed treatment is proportionate to your report or test result, what maintenance costs follow, and how the kitchen layout will work.