The conventional testing methods used by the Regional Joint Office to investigate water seepage cases include moisture monitoring at seepage locations, colour water test for drainage pipes, ponding test and water spray test for floor slabs and walls as well as reversible pressure test for water supply pipes. Depending on the seepage situations, each case may involve one or more of these testing methods.

Since June 2018, JO has applied advanced testing technologies, such as microwave tomography and whenever necessary, infrared thermography, in professional investigation in selected pilot districts where applicable. In cases where these advanced technologies cannot be effectively applied (such as small seepage area, spalling of concrete ceilings affected by water seepage or blockage by tile finishes or other facilities (including suspended ceiling or pipes, etc.) on the ceiling, conventional methods will be carried out.

Microwave Tomography (MT):

Principles

Microwave scanning utilises electromagnetic wave at microwave frequencies to detect the presence and distribution of water molecules in concrete. Water molecules possess a much higher dielectric constant as compared to those of other cementitious material in concrete. This allows it to obtain data reflecting the amount of moisture in concrete floor slabs.

Advantages

1. Non-destructive test
2. Eliminates the need to enter suspected premises (usually the premises directly above) for investigation, reducing the time required compared to conventional methods
3. The path of water flow could be deduced with the microwave tomographs measured at different depths by various probes.

Infrared Thermography (IT):

Principles

IR thermography detects emitted radiation in the infrared range of the electromagnetic spectrum. IT is used to evaluate any presence of water seepage based on the difference in surface temperature between the testing surface of the seepage area as compared to the nearby dry areas. IT detects the extent and location of the seepage area from the infrared thermographic images.

Advantages

1. Non-destructive test
2. Eliminates the need to enter suspected premises (usually the premises directly above) for investigation, reducing the time required compared to conventional methods
3. Non-contact technique, making it applicable to areas with accessibility issues (e.g., high headroom conditions)

Mainly for detecting the extents of areas affected by seepage