Key points
- Meter test: note the reading, use no water for two hours; if it changes, you probably have a leak.
- Toilet test: a few drops of food colouring in the cistern; if colour shows in the bowl within 10 minutes, it leaks.
- A tap dripping once a second wastes more than 3,000 gallons (about 11,000 litres) a year.
- Thermal cameras pick up the evaporative cooling of wet materials, but they show surface temperature only; confirm with a moisture meter.
A hidden leak is worse than a visible one: it raises the bill, ruins paint and tiles, feeds mould, and can reach the reinforcing steel (see rebar corrosion). The US Environmental Protection Agency estimates the average household's leaks can waste more than 9,300 gallons a year (about 35,000 litres), and that fixing easily corrected leaks can save about 10% on water bills1.
1) Tests you can do yourself (free)
The meter test
- Turn off every tap and appliance that uses water (washing machine, filling water heater, pump, irrigation).
- Note or photograph the water meter reading.
- Wait two hours without using any water.
- If the reading changed, you probably have a leak1.
If you have a ground tank and pump, the meter measures what enters the tank. Close the valve after the meter, or watch the tank level and the pump; a pump that keeps cycling with no use signals a leak after it (practical note).
The toilet test
Put a few drops of food colouring in the toilet cistern; if colour shows in the bowl within 10 minutes without flushing, there is a leak1. The usual cause is a flapper or float valve that needs replacing.
Taps and showers
A tap dripping once a second wastes more than 3,000 gallons a year (about 11,000 litres), and a showerhead leaking 10 drips a minute wastes more than 500 gallons a year1.
2) Signs of a hidden leak
- Damp, peeling paint or white salt deposits on a wall next to a bathroom or kitchen. See paint problems.
- Hollow-sounding or lifting tiles, or dark grout that never dries.
- Stains on the ceiling below an upstairs bathroom.
- A persistent musty smell.
- The sound of running water with all taps closed.
3) Professionals' tools and their limits
| Tool | How it works | Limits |
|---|---|---|
| Thermal (IR) camera | Evaporative cooling of wet materials is usually the strongest indicator the camera picks up, locating moisture without breaking anything2. | It displays apparent surface temperature differences only3; confirm with a moisture meter (practical advice). |
| Moisture meter | Used to confirm the initial diagnosis4. | Can lead to misdiagnosis depending on the material and the building's condition; should not be relied on alone4. |
| Acoustic listening devices | Pick up the sound of pressurised water escaping from pipes. | Less effective on (unpressurised) drain pipes. |
| Pressure test | Isolate part of the network, pressurise it and watch for pressure loss. | Shows that a section leaks, not exactly where. |
4) Before hiring a leak detection company
- Ask which tools they will use (thermal camera, moisture meter, pressure test) and ask for a photo report.
- Ask them to identify the cause and location before breaking anything, with an estimate of how much will be opened up.
- Agree in writing: is the price for detection only, or detection and repair? Who reinstates tiles and finishes?
- Ask for a warranty on the repair.
Sources
The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.
- 1Fix a Leak Week — How to check for leaks (meter test, toilet dye test) — U.S. EPA — WaterSense
- 2Why thermal imaging is essential for detecting moisture damage — Fluke Corporation
- 3Thermal Imaging Infrared Building Inspection Guidebook — Fluke Corporation — technical guidebook
- 4Diagnosing the causes of dampness in buildings — BRE (Building Research Establishment)