Which of the following can adversely affect the results of a leakage test?

Temperature can significantly affect the results of a leakage test due to its influence on the viscosity of water and the conditions of the materials involved. As temperature fluctuates, it can lead to changes in the flow rate, expanding or contracting the piping materials, which may create gaps or seal imperfections that wouldn't be present under consistent, moderate temperatures. Consequently, if the temperature is too high or too low, it may result in skewed leakage test outcomes, providing either false positives or negatives regarding the integrity of the drain system.

In contrast, factors like soil composition, drain width, and water pressure play critical roles in the overall design and operational effectiveness of a drainage system but do not have the same direct impact on the test itself in terms of immediate leakage detection performance.