Smoke test
|
|
A smoke test is used to find leaks in pipes and containers. Artificially created smoke is forced into the pipe or container. Plumes of smoke form where there are defects. It is particularly useful where completely sealing the system is not practical such as ventilated sanitary sewer systems.
The term smoke test is used in electronics to refer to the first time a circuit under development is attached to power. This may be done before all the work is complete, just to ensure that there are no major flaws that would make further work moot. Circuits that fail at this stage sometimes literally produce smoke, often from burning resistors, which produce a unique smell familiar to many technicians.
The term is also used metaphorically, especially in computer programming, where it is an entry to further testing.
Smoke Testing of Plumbing and Sanitary Sewer Systems
Non-toxic smoke is used to find leaks in plumbing and sanitary sewer systems.
Smoke Testing of Sewer Systems
Smoke testing of sanitary sewer systems is primarily used to find places where ground water and storm runoff can enter the sanitary sewer system.
When smoke testing a sanitary sewer system it is helpful partially block off the section of sewer to be tested. This can be done by using a sand bag on the end of a rope. The sand bag is lowered into the manhole and swung into position to partially block lines. Completely blocking the line can cause water to back up and prevent smoke from escaping through defects. Smoke testing should not be done after rain or when ground water is unusually high as this may also prevent detection of defects.
Large downdraft fans, usually with gasoline engines, are placed on top of open manholes at either end of the section to be tested. If possible all lines in the manholes except for the line between the manholes are partially blocked. A smoke bomb is lit and placed on a grate or in a holder on top of each fan. The fans create a pressure differential that forces the artificial smoke into the sewer at a pressure just above atmospheric. With properly installed plumbing the traps will prevent the smoke from entering the house and redirected it out the plumbing vents.
Defective plumbing systems or dry traps will allow smoke to enter the inside of the house.
The area around the section being tested is searched for smoke plumes. Plumes coming from plumbing vents or the interface between the fan shroud and manhole rim are normal however smoke plumes outside of the manhole rim are not. Plumes are marked, usually with flags, and defects are noted using measurements from stationary landmarks like the corners of houses. The plumes or markers may also be photographed.