Other Types of Drain Survey
Although a CCTV survey is the most commonly used method of establishing the condition of a below-ground drain it is not the only method. Depending on the initial investigation purpose or the results of a CCTV survey other forms of survey, inspection or testing might be required.
If the drainage installation is new (or recently repaired) Local Authority Building Control will require the results of an air test. This is where the new drain is pressurised and monitored. An excessive drop in pressure would result in a failure.
A water test is very similar, but in this case, designed for older drains that are unlikely to pass an air test. In this scenario, the system is filled with water at low pressure and left for a specified period of time. Water loss is then measured to determine a pass or a fail.
In both cases the watertight integrity of the drain is being tested. Water tightness is an important aspect of a below-ground drainage system. As well as signifying issues on rigid pipes, such as cracks and fractures, which might lead to blockages, lack of water tightness may be due to poor joints. Joint issues can be significant as they might not be readily visible but will lead to exfiltration and subsequent erosion. This can eventually lead to pipe movement and more serious issues. For example, if the drain is close to a building’s foundations, soil erosion might lead to subsidence.