← Buyer GuidesHow to Read an RO Spec Sheet (Without Getting Fooled)
An RO spec sheet is only as honest as its test conditions. This guide shows which numbers matter, which need context, and which are marketing.
Key points
- GPD without test conditions is marketing. Ask: at what pressure, temperature, and feed TDS was it measured?
- Rejection rate and GPD trade off against each other — a huge GPD with no rejection figure is a red flag.
- Dimensions must match your installation: check housing sizes, not just 'under-sink'.
- 'NSF certified' needs a certificate number you can verify in the NSF database — 'NSF tested' is not the same.
- Operating limits (max feed TDS, temperature range, pH range) tell you where the system will fail — read them first.
Action checklist
- Circle every number missing its test conditions and ask for them.
- Verify certification numbers in the public NSF / CE databases.
- Compare dimensions against your cabinet/market requirements.
- Check the fine print on operating limits (feed TDS, temperature, pressure).
- Confirm the BOM behind the sheet: membrane brand, fitting brand, housing material.
- Keep the signed spec sheet as an annex to the purchase contract.
Common questions
The sheet says 800 GPD. Should I believe it?
Believe it with conditions attached: 800 GPD at the stated pressure/temperature/feed-TDS, on a new membrane. In real kitchens with lower pressure, expect less. Size your product choice on realistic conditions, not the headline number.
Related reading
A note on honesty. CWS provides sourcing and QC services for water purification products. This guide is general information for overseas buyers — not a guarantee of any outcome. We don't promise the lowest price in China, and we don't promise zero defects. What we do promise: written inspection criteria, lot traceability, and telling you when something is outside what we can verify.