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Underground water leaks contribute to high water bills – Water leak detection how do we do it?

Author: Graham Mann, Water Audit Expert.

Most businesses are billed for water and waste water based on volume recorded on a water meter. The example in the picture is a 50mm water meter fitted to a 50mm water supply pipe. All water that passes through the water meter is recorded on the dial in litres and cubic metres.

Having had a water audit completed by a water audit expert if the water audit report has determined there is an underground water leak a water leak detection engineer is appointed. If water network plans are available water leak detection commences using sounding techniques  as water leaks transmit audible sound through water pipes and water fittings such as isolation valves. In the first example picture below a highly sensitive microphone is placed on or near the suspect water pipe, any leak noise is amplified and an experienced leakage engineer can normally determine very near or sometimes the exact position of the water leak.

If the water leak is proving very difficult to locate due to low level noise then trace gas techniques are used as you can see from the picture below, a gas mixture of 95% nitrogen and 5% hydrogen is used. Hydrogen is the lightest and smallest molecule in the atmosphere and so will exit the water leak in the pipe and rise to ground level where the escaping gas is detected by a sensitive gas detection kit combined with the leak detection engineers expertise the leak location is marked down for water leak repair.

Water leak detection using leak noise correlation – when water escapes from a pipe it produces a sound pressure wave, the leak noise sound travels along the water pipe from the damaged pipe, the leak noise velocity depends on water pipe size, material and ground conditions. When the area of the water leak / leaks has been determined a sensor will be placed either side of the suspected water leak, the sensors are normally placed either on the pipe or on the isolation valves located either side of the leak noise. The leakage engineers then sets up the system inputting details such as water pipe material if known, pipe dimensions then each sensor records the sound made by the water leak and transmits this data to a base unit which when viewing the leak noise on screen  will in most cases calculate the exact location of the water leak, this is then marked down for water leak repairs.

Water leaks can go unnoticed for months even years and in some cases a leak could be 60% of your total water bill!