Two concepts to keep separate
In pharma, "water" falls under two systems:
- Production water: purified water and WFI used in manufacturing, tightly regulated under the Pharmacopoeia and GMP, supplied by dedicated generation systems.
- Laboratory water: used in the QC lab for testing, standards and rinsing. It does not enter product, but the reliability of test data depends on it.
This article addresses the latter — though note that laboratory water quality directly affects release decisions, so inspectors do look at it.
What inspectors typically examine
- Whether water quality meets method requirements. Each method specifies a grade (HPLC methods generally require Grade 1 water). You need to be able to demonstrate your water meets it.
- Inline monitoring and records. Are resistivity and TOC logged continuously? Can you trace water quality to a specific day and batch of testing?
- Consumable replacement plans and records. On what interval are cartridges, UV lamps and final filters changed, on what basis, and is it documented?
- How excursions are handled. What happens to test results from periods when water quality was out of specification? Is there a deviation record?
- Calibration and maintenance. Intervals and records for inline instrumentation.
Records are where labs most often fail
Many labs have sound equipment and still fail — because they cannot produce the records. Typical cases:
- A UV lamp replaced only when it failed, with no interval record → cannot demonstrate water quality was acceptable beforehand.
- Water-quality monitoring showing only the current on-screen number, no history → nothing to reconstruct during traceability exercises.
- Cartridge changes performed but not documented → as far as an inspection is concerned, they did not happen.
So at selection, data logging and exportability is a requirement, not a bonus feature.
Practical day-to-day management
- Maintain a water-quality log. Record resistivity (with temperature) and TOC daily; microbiological counts weekly where applicable.
- Consumable schedule. Set replacement intervals from manufacturer guidance plus your own data, write them into the SOP and keep records.
- Fixed sampling points. Specify where to sample, in what container, and how much — written into the SOP to remove operator variability.
- Excursion procedure. Define which tests to suspend and how existing results are re-verified when quality is out of specification, with deviation records.
- Calibrate instruments on schedule. Verify inline resistivity/conductivity probes against standard solutions periodically.
Compliance-related selection criteria
- Data logging and export. Can it record historical water quality and export it in an archivable format?
- Traceable events. Can consumable changes be flagged so the quality curve lines up with maintenance actions?
- Material compliance. Do wetted materials carry the declarations your system requires (e.g. USP Class VI, FDA-related)? Request the documents.
- Verifiability. Can the vendor support IQ/OQ documentation?
Whether each is mandatory depends on your quality system tier, but establish at selection whether it can be provided — do not discover the gap the week before an inspection.
One reminder
A GMP inspection does not pass because of the brand on your instrument. It looks for an evidence chain proving water quality is continuously controlled. Equipment is one link; records and SOPs are the other two.
