After installation of sewer; Sewer Test is subjected before they are put into service. Therefore sewers are under gone through the following tests (i) Test for straightness of alignment and obstruction (ii) Water test (iii) Smoke test (iv) Air test. Let us discuss each test in detail along with test procedures, apparatus and their dimensions, and many more.

Read – what are the types and shapes of sewer?

(i) Test for straightness of alignment and obstruction

As soon as a stretch of sewer is laid, then it is tested for straightness and obstruction. It has two method, described below –

1. At the high end of sewer or drain, a smooth ball of diameter 13 mm less that the pipe bore is insert. If there is no obstruction in the form of yarn or mortar projecting through the joint, then the ball will roll down the invert of the pipe. Thus emerge at the lower end. Alternatively a double disc or solid closed cylinder 75 mm less than internal dimension of the sewer may run. The run through the stretch of the sewer, ensures that it is free from any obstruction.
2. A mirror is placed at one end of the sewer line; lamp at other end. If the pipe line is straight, the full circle of light will observed in mirror. If the pipe line is not straight, this would apparent. The mirror will also indicate any obstruction in the pipe-barrel.

(ii) Water test

Water test is carried out to find out the water tightness of the joints. Sewer Test is carried out after giving sufficient time for the joints to set. In case of concrete and stoneware pipes with cement mortar joints, pipes should be tested three days after the cement mortar joints have been made. If is necessary that the pipelines are filled with water for about a week before commencing the application of pressure to allow for the absorption by the pipe wall.

The sewers are tested by plugging the upper end with a provision for an air outlet pipe with stop cock. The water is filled through a funnel connected at the lower end provided with a plug. Afterwards the air is expelled out, stop cock is closed and the reading is noted after 30 minutes. The pipe line is then inspected. There should not be any leaks in the pipe and joints. Water shall not exceed 15 ml in the smaller dia. and 60 ml in the larger dia. of length 100 mm. Any sewer or part of it; not meeting the test, shall be emptied and repaired and tested again.

(iii) Smoke test

Smoke test is carried out for drainage pipes located in buildings. Thus smoke is produced by burning oil, waste, tar, paper etc. in the combustion chamber of the smoke machine. The pipes are approved gas-tight by the smoke test conducted under pressure of 25 mm of water. It is maintained for 15 minutes after all trap seals have been filled with water.

(iv) Air test

Air testing becomes necessary, particularly in large dia. pipes when the required quantity of water is not available for testing. It is done by subjecting the stretch of pipe to an air pressure of 100 mm of water by means of a hand pump. The pressure is maintained at 75 mm. The joints shall be assumed to be water tight. In case the drop is more than 25 mm, the leaking joints shall be traced and suitably treated to ensure water tightness. The exact point of leakage can be detected by applying soap solution to all the joints in the live and looking for air bubbles.

Benefits of using Sewer Test

• Save time with the ready to go system
• Provides guarantee to operate system safely
• A positive test for in-filtration or ex-filtration
• Testing can be performed on various types of sewer pipe including newly installed or however pre-existing lines
• Also cost effective solution
• Verifies the integrity of new sewer lines
• Simple, fast and efficient quality control tests
• Can also verify workmanship of newly installed sewer lines