The pneumatic test for drains was introduced in the early 'eighties, and consists of plugging all the drain openings and filling them, as well as the manholes and soil pipes, with air under a slight pressure. The test is troublesome to apply in a thorough manner, and defects and leakages arc not localised by it. The smoke test is far preferable, as by it defects are more readily traced to then-position by the senses of sight and smell.