Find leaks by measuring the flow leaving the tank late at night with every tap closed: any flow is going to leaks, and a loss under 10% of the supply is acceptable, 10-25% needs attention and over 25% is critical. Then walk the pipe route looking for wet spots, green patches and erosion, and close sections one at a time until the flow from the tank stops.
Part of Water Distribution
Leak detection is the routine of measuring and locating water lost from a distribution network before it reaches a tap. Every system leaks; the question is how much.
Every System Leaks, So Measure It
A pipe network loses some water at joints, fittings and cracks. Left alone, small leaks grow, waste a source that may be limited, and drop the pressure at the end of the line. They can also let dirty water in when the pressure falls.
The water-distribution page sets three bands for the share of water lost between source and taps:
| Loss | Status |
|---|---|
| Under 10% | Acceptable |
| 10-25% | Needs attention |
| Over 25% | Critical: a quarter of your water is wasted |
What You Need
- A way to measure flow at the tank outlet or the source: a container and a clock (Flow Measurement)
- Valves that let you close sections one at a time (Isolation Valves)
- A map of the pipe route
- Time, late at night when nobody is drawing water
- Spare fittings and a pipe cutter, for repair on the spot
Method: Measure, Walk, Narrow Down, Fix
Step 1: Measure at night. With all taps closed, collect the water leaving the tank outlet in a container and time it. Any flow is leakage.
Step 2: Work out the loss share: leak flow ÷ total daily supply.
Step 3: Walk the route (Visual Inspection).
Step 4: Close sections one at a time. When the tank outlet stops flowing, the leak is in the last section you closed.
Step 5: Fix it. For PVC, cut out the damaged section and fit a repair coupling. For HDPE, use compression fittings or barbed repair couplers.
Step 6: Measure again to see if the loss has fallen.
Worked Example
A night test: 20 L collected in 30 minutes. That is 20 ÷ 1,800 s = 0.011 L/s, or 0.011 × 86,400 = 960 L/day. If the system supplies 4,000 L/day, the loss is 960 ÷ 4,000 = 24%, in the “needs attention” band, close to critical. After a fix, a repeat test of 4 L in 30 minutes is 4 ÷ 1,800 × 86,400 = 192 L/day, which is 192 ÷ 4,000 = 4.8%, acceptable.
Common Mistakes
- Testing while someone draws water. A tap in use hides the leak.
- A float valve left dripping. The tank refills continuously, hiding the loss.
- Digging at a wet spot before closing the valve. A pressurised leak washes out the ground.
- No retest. You can’t tell whether the repair worked.
Safety
A repaired pipe needs flushing
A leak that lets water out can also let dirty water in when the pressure drops. After a repair, flush the section until the water runs clear, and treat the water as suspect until it has been tested (Community Water Testing).
What’s Next
- Learn next: Visual Inspection — walking the line
- Combine with: Flow Comparison — measuring loss between two points