Formula and example
How it is calculated
Litres/hour = drops/minute × ml/drop × 60 / 1,000; or collected ml / 1,000 × 3,600 / collection seconds. Annual m³ = litres/hour × hours/day × days/week / 7 × 365 / 1,000. Annual cost = annual m³ × (water price + wastewater share/100 × wastewater price).
Worked example
60 drops per minute at 0.25 ml per drop lose 0.9 litres per hour. If the tap drips all day, every day, that is 21.6 litres per day and 7.884 m³ per year. At water and wastewater prices of 300 and 500 currency units/m³, with all the water charged for wastewater, the annual cost is 6,307.20 currency units.
Things to check
- The 0.25 ml drop size is an editable approximation. This calculator estimates the loss; it cannot identify a faulty part or determine how to repair it.
- Prices of 300 and 500 are illustrative inputs, not local tariffs. Enter the usage-based charges from your own bill and use the same currency throughout. Fixed standing charges and water heating are excluded.
- Daily results are averages across the week. The monthly estimate covers 30 days and the annual estimate 365 days, with the same leakage rate, schedule and prices throughout.
- Repair payback assumes the repair stops the whole measured loss. It excludes interest, future price changes and any damage caused by the leak.
Frequently asked questions
How can I measure a slow drip?
Collect the water in a measuring container for a known period, such as five or ten minutes. Enter the collected volume in millilitres and the duration in seconds.
Are all drops the same size?
No. Drop size varies with the tap and the way the water drips. The drop-count method is an approximation; adjust the volume or use a collected-water measurement.