Standard Operating Procedure: Measuring Flow Rates

Equipment:

• Calibrated container (5 L capacity recommended)

• Stopwatch or timer (accuracy ±0.1 s)

• Marker or tape (to clearly indicate container’s fill line)

• Pen and log sheet (for recording results)

Flow rates of appliances like faucets and showerheads can be measured in two ways:

1. Use a flow meter and follow manufacturer’s instructions (cost: approx. 20 €)

2. Use a bucket and a stopwatch

Procedure Steps for using a Bucket and Stopwatch

Step 1: Set Up

• Place the calibrated container directly under the tap spout.

• Mark the exact fill-line on the container (if not pre-marked).

• Have your stopwatch and log sheet ready.
  

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Step 2: Start Flow

• Open the tap to its maximum flow setting.

• If measuring mixed flow, open both hot and cold taps fully.
  
  

Step 3: Measure

• As soon as water begins to fill, start the stopwatch.

• Stop the stopwatch the instant the water reaches the fill-line.

Step 4: Record Time

• Note the elapsed time (in seconds) on your log sheet.

• Calculate Flow Rate

  • Formula: Flow Rate (L / min) = (Container volume (L) / Time (s)) x 60

  • Example:

    • Volume = 5 litres

    • Time = 30 seconds

    • Flow rate = 5/30 x 60 = 10 litres/minute
      

Step 5: Repeat & Average

• Perform three measurements at each fixture.

• Calculate the average to account for minor variations.
  

Step 6: Document

• Record each trial’s time and calculated flow rate.

• Note any anomalies (e.g. air in lines, temperature fluctuations).

• File the completed log sheet in the maintenance records.
  

Step 7: Review

• Compare measured flow rates against performance benchmarks.

• Schedule corrective actions (e.g. aerator replacement) if flow exceeds or falls below target values.