← Buyer GuidesHow to Handle Defective Filters After Delivery
Some defects only surface after installation — a small percentage is normal in manufacturing. What separates good suppliers is the process for handling them, agreed before shipment.
Key points
- Define 'defective' in the contract: dead-on-arrival, early-life failure window (e.g., 90 days), and the evidence required (photos, serial numbers).
- Standard practice: 1–2% spare parts shipped with the order to cover field replacements without air freight.
- Root-cause process matters more than refunds: ask how the factory traces a defect back to a lot, line, or component batch.
- Keep failed units (or key parts) for the supplier's analysis — photos alone often can't diagnose.
- We can't promise zero defects. We promise a written process, lot traceability, and spares on the water with your order.
Action checklist
- Write the defect definition and claim window into the purchase contract.
- Agree the spare-parts percentage and ship them WITH the order.
- Set up lot-number traceability (carton labels → production records).
- Define the claim flow: evidence needed, response time, replacement vs credit.
- Keep a small failure log per SKU — patterns beat anecdotes.
- Review defect rates quarterly with the factory; don't wait for a crisis.
Common questions
What defect rate is 'normal' for filters?
Well-run lines typically see low single-digit percentages for minor issues and near-zero for critical ones. If your field failure rate climbs above a few percent, treat it as a systemic problem, not bad luck — and trigger the root-cause process.
Should I ask for a warranty?
Yes, but read what it actually covers: duration, who pays return freight, and whether it's replacement, credit, or repair. A warranty without a claim process is a paragraph, not a promise.
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.