A purified water system is never finished — it is either maintained or quietly heading out of specification. These habits keep the water boring, which is exactly what water should be.
Trend the numbers, do not just record them
Conductivity and TOC readings belong on a trend chart, not in a drawer. A loop that creeps from 0.6 to 0.9 µS/cm over six weeks is telling you something a single in-spec reading never will. Set review thresholds tighter than alert limits, and investigate slopes, not just breaches.
Keep the water moving
Biofilm negotiates with stagnant water and loses against turbulent flow. Verify loop return flow against its design value monthly, exercise rarely used points on a schedule, and treat any dead leg longer than the guideline as a finding to engineer away, not a note to file.
Sanitise on schedule, verify on evidence
Hot-water sanitisation only counts if the coldest point of the loop reached temperature for the full hold time. Log return temperature through the cycle and keep the curves with the batch records — the curve is the evidence, the calendar entry is just the intention.
Respect the pre-treatment
Most RO and EDI problems are born upstream: an exhausted softener, a fouled prefilter, a feed temperature nobody watched. Daily checks on pre-treatment take five minutes and prevent the expensive kind of surprise at the membrane end.
