A drain depth gauge is a simple graduated rod, weighted line or laser instrument used to measure the depth from a known surface datum to the invert level of a pipe inside an inspection chamber. The reading allows engineers to record falls along a drain run, to design connections to new pipework and to identify chambers that have become silted or undersized. Modern laser depth gauges replace the traditional metal-tape method, giving fast and accurate readings without leaning into the chamber. Use of a depth gauge supports compliance with the Confined Space Regulations 1997 by avoiding entry. Accurate invert level data is essential for designing new lateral connections, new gullies and SuDS interventions to BS EN 752 and Building Regulations Part H.
Drain depth gauge
Instrument used to measure invert depth at an inspection chamber.
