Factory Water Balance: Intake, Reuse and Unexplained Loss

A factory water balance compares external water input with water leaving the boundary and the change in stored water over the same period. Track internal reuse separately so recirculated water is not counted as new intake, and investigate any unexplained difference.

A monthly water bill cannot explain what happened inside yesterday’s shift. Start with a balance the utility lead can reconcile: where water entered, where it left and what remained in storage.

Draw the boundary and align the readings

The US EPA’s Lean and Water Toolkit describes facility water balances as a way to understand inputs and uses. Start with one facility or process boundary. Mark incoming supplies, transfers across that boundary, discharge points and storage. Keep the period, units and reading times consistent.

The utility lead owns the balance; operators capture meter and tank readings, and process owners explain water carried in product or otherwise consumed. Label each quantity measured, calculated or estimated. A tanker invoice from last week cannot stand in for today’s intake.

Reconcile a daily example

Illustrative scenario: the factory boundary includes its treatment and reuse loop. Opening and closing readings cover the same 24 hours. All volumes below are invented and expressed in cubic metres.

Five cubic metres remain unexplained. That is a balance discrepancy, not proof of a five-cubic-metre leak. Meter timing, estimated evaporation, an unrecorded transfer or a tank-volume conversion may explain part of it. The 40 cubic metres reused inside the boundary appear neither as new external intake nor as an external output.

Use a reading record that can be checked

For every meter, retain its ID, location, unit, multiplier, opening and closing value, timestamps and reader. For storage, retain the measurement and the approved conversion to volume. A meter replacement or reset needs the old final reading, new initial reading and handover time.

Record known transfers even when they cross another team’s area rather than the public boundary. When producing a process-level balance, a reused flow entering that smaller process can be an input. At whole-factory level, the same flow may be internal. Write which balance is being reported before adding the volumes.

Investigate the difference in a useful order

First align units and time cut-offs. Then review resets, missing readings and storage changes. Ask process owners to check the assumptions behind estimated consumption. Only after those checks should the team assign the remaining discrepancy to a physical investigation.

A missing discharge reading keeps the balance provisional. Show the measured subtotal and a labelled estimate if the owner has an agreed basis; do not insert whatever number makes the total match. Backfill the reading with its source and retain the earlier provisional version.

Agree an investigation threshold suited to meter resolution and the uncertainty of estimates. There is no universal acceptable loss percentage in this worksheet. Close the day when every flow has a basis, each difference beyond the chosen threshold has an owner and due date, and corrections retain their original evidence.

Use the balance to choose a specific next investigation

If the largest uncertainty is an unmetered cleaning supply, improve that record before promising savings. If matched non-production periods repeatedly show unexplained intake after data checks, assign an inspection to the utility team. Compare equivalent operating conditions and separately record changes in output, cleaning and weather-dependent demand.

In Optiwise, our no-code forms, formulas and related records can hold readings, storage calculations and exception actions. Connect them to production context when comparing batches or shifts. The measurement method and suitability of any connected instrument remain specific to the site.

Water-balance questions

Can reused water be added to fresh intake to report total water purchased?

No. Purchases and external intake are separate from water circulating inside the selected boundary. Report reuse as its own measure with a stated measurement point.

Does an unexplained balance prove a leak?

No. Check timing, units, storage, missing flows and estimates first. Investigate the remaining difference and record the evidence before assigning a cause.

Bring one day of water readings to an Optiwise demo to build the balance and its exception register.