The sewers after being laid and jointed are tested for watertight joints and also for correct straight alignment as described below
- Test for Leakage
- Test for Straightness of Alignment and Obstruction
Types of Sewer Tests
1. Sewer Testing for Leakage (Water Test)
The sewer testing is ensure no leakage through the joints after giving sufficient time to these joints to set in. For this purpose sewer pipe sections are tested from manhole to manhole under a test pressure of 1.5m of water head i.e. depth of water in the manhole is maintained at about 1.5m. The lower end of the sewer is first of all plugged.
The water is then filled in the manhole at the upper end and is allowed to flow through the sewer line. The sewer line is watched by moving along the trench and the joints which leak or sweat are repaired. The leakage pipe if any will also be replaced.
2. Sewer Testing for Straightness of Alignment and Obstruction
The straightness of the sewer pipe can be tested by placing a mirror at one end of the sewer line and a lamp at the other end. If the pipe line is straight, the full circle of light will be observed. However, if the pipe line is non-straight, this would be apparent and the mirror will also indicate any obstruction in the pipe barrel.
Any obstruction present in the pipe can also be tested by inserting at the upper end of the sewer a smooth inserting at the upper end of the sewer a smooth ball of diameter 13mm less than internal diameter of the sewer pipe. In the absence of any obstruction, such as yarn or mortar projecting through the joints etc. the ball shall roll down the invert of the sewer pipe and emerge at the lower end.