An AQL value is one input to an acceptance-sampling plan; it is not a promise that a lot contains that percentage of defects or that every defect will be found. For shower hardware, a usable plan defines the lot, sampling standard and edition, defect criteria, inspection method, decision rule and response to a failed lot before production is released.
Choose the standard and edition explicitly
ISO published the third edition of ISO 2859-1:2026 in January 2026. It replaces the 1999 edition and amendments. A purchase order or inspection agreement should name the edition and sampling scheme it uses. If an existing contract names an older edition, agree in writing whether and when the plan will change; do not silently substitute a new table.
ISO 2859-1 provides AQL-indexed sampling schemes for lot-by-lot inspection. The applicable sample size and acceptance/rejection numbers depend on the selected scheme and inputs such as lot size, inspection level, inspection severity and AQL. Use the applicable table in the purchased standard or a controlled licensed implementation. Do not reuse a sample-count example without checking those inputs.
Define the lot before selecting a sample
Write down what counts as one lot: product family and SKU, finish, production period, factory or line, drawing revision, packaging configuration and quantity. If a shipment mixes materially different versions, agree whether it will be separated into lots. The sample should be selected randomly from the defined lot by an identified inspector; hand-picked samples can hide variation.
Then record the scheme inputs and inspection stages: normal, tightened or reduced inspection where applicable; single, double or other scheme; sample selection; and the rule for changing inspection status after results. A plan should also say who may authorize a change and how it is recorded.
Write defect criteria around the approved specification
Classify defects in the agreement, with photographs or measurable acceptance criteria where possible. The categories below are examples to adapt to the product and risk review, not a universal classification:
- Potential safety or regulatory issue: define an immediate hold, escalation and investigation process. A sample-based plan cannot establish that no unsafe unit exists; specify additional controls or 100% checks where the risk assessment requires them.
- Fit or function: use the approved drawing and product instructions to define relevant dimensions, glass compatibility, operation, fastening and finish criteria.
- Appearance or packaging: define the approved finish reference, inspection lighting and viewing distance, acceptable variation, labels, carton condition and packing configuration.
AQL is not the percentage of defective product that a buyer must accept. It indexes a sampling plan’s acceptance and rejection rules; a particular sample may pass or fail, and sampling does not guarantee the quality of every unit. Keep safety and regulatory acceptance requirements separate from cosmetic or fit criteria. The sample approval process helps establish the reference drawing and finish.
Make inspection repeatable
For each check, identify the instrument or method, the specification revision, sample size source, result field and responsible person. Depending on the product, checks may include:
- SKU, finish code, markings, packaging and included components against the approved order.
- Dimensions and glass-interface features checked against the current drawing using suitable calibrated equipment.
- Operation and assembly checks performed using the product’s approved inspection method.
- Visual finish comparison against an agreed physical reference under recorded lighting conditions.
- Review of separate production-test or laboratory reports, with the exact model, configuration, method and tested sample identified.
Sampling for final inspection does not replace process controls or product-specific testing. Avoid destructive or load tests on installed or tempered glass unless the method and equipment were designed for that test.
Agree what happens when a lot fails
The purchase order should say whether a failed lot is held, sorted, reworked, returned, replaced or subjected to a new inspection after corrective action. Identify who approves disposition, who pays for inspection and freight, what records are required, and whether the first failure changes future inspection status. Define how nonconforming product is contained so it is not mixed with accepted stock. A second sample should follow the written plan; it should not be chosen informally to overturn an inconvenient result.
Put the plan in the purchase order
For each order, attach the approved drawing and revision, lot definition, named standard and edition, scheme inputs, defect criteria, inspection checklist, sampling method, report format, failure response and authorized approvers. Review the plan when the design, process, supplier, market requirement or risk assessment changes. The shower hardware RFQ checklist can help collect the product requirements before a quotation is finalized.
Frequently Asked Questions
What AQL should I use for shower hardware?
There is no universal AQL for every part or buyer. Select values and additional controls from the product risk, specification, customer requirements and agreed acceptance plan, then document them before inspection.
Does AQL 2.5 mean I can accept 2.5 percent defective products?
No. AQL is an index used in a sampling scheme; it is not a guaranteed lot defect rate or permission to ship a known defective unit. The selected plan determines sample and lot decisions.
How many pieces should be inspected from a 1,000-piece order?
The sample size cannot be selected from lot size alone. It also depends on the named standard edition, scheme, inspection level and other plan inputs. Use the applicable current table and record the selected plan.
Can sampling prove that no unsafe item is in a lot?
No. Sampling leaves a risk that defects remain undetected. Use the product risk assessment to set escalation, containment and any additional checks needed for safety or regulatory characteristics.
What should happen after an inspection failure?
Hold the affected lot, document the findings, investigate the cause and follow the pre-agreed disposition and reinspection rules. Keep the corrective-action and release approval with the lot records.