How to Write a Water Treatment Equipment Specification: A Buyer's Guide
Why specifications fail — and how to fix them
Equipment procurement failures in water treatment fall into three categories: underspecified (the supplier delivers what was asked but it doesn't do what was needed), overspecified (the specification is so prescriptive that it limits competitive response and drives up cost), and unverifiable (the specification includes performance requirements that cannot be tested at commissioning). All three are avoidable with disciplined specification writing.
Structure of a minimum viable specification
A minimum viable equipment specification for water treatment should include:
- Scope: what is and is not included in the supply (skid assembly, instrumentation, controls, commissioning, training, spare parts).
- Design conditions: feed water quality (TDS, turbidity, SDI, temperature range, pH, target contaminants), design flow rates (maximum, minimum, normal), and operating hours per year.
- Performance requirements: permeate quality targets (TDS, SDI, turbidity), recovery ratio, energy consumption at design point, and maximum allowable fouling rate.
- Standards compliance: applicable standards (NSF/ANSI 61, ASME, PED, ATEX if relevant, local electrical codes).
- Acceptance testing: site acceptance test (SAT) protocol, performance test duration (minimum 72 hours at design conditions), pass/fail criteria, and remedy provisions.
The role of a Request for Quotation (RFQ)
An RFQ translates the specification into a structured request for supplier response. Effective RFQs require suppliers to complete a technical data sheet (not just confirm compliance), provide a process flow diagram with operating point, identify consumable replacement schedules and costs, and confirm warranty terms for membranes, pumps and instrumentation separately. Suppliers who cannot complete the technical data sheet as specified should be rated down in evaluation — the inability to complete it at tender is a reliable predictor of the inability to support the system in service.