Straightness, Obstruction, Air & Water Test

 

This article will discuss the Testing of Sewer After Laying Pipe.

A sewer is an underground conduit or a pipe ( generally closed but normally not flowing full ) used to convey sewage to the point of disposal or discharge. 

After laying the pipe, the sewer should be tested before backfilling and finishing. Sewers are usually subjected to the following test:

i. Straightness test

ii. Obstruction test

iii. Air test

iv. Water test

 

 

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  Testing of Sewer After Laying Pipe  

 

 

  i. Straightness test  

A straightness test is done by placing a mirror at one end of the sewer and a lamp at the other.

If a pipeline is straight, the full circle of light can be observed otherwise apparent.

 

 

  ii. Obstruction test  

By inserting a smooth ball of diameter 13 mm from the upper end and letting it roll downward.

If there is no obstruction in the sewer line, the ball shall roll down the pipe’s invert and emerge at the lower end.

 

 

  iii. Air test  

If there is no sufficient water and the size of the pipe is larger, air testing is done by plugging the sewer at both ends.

From one end, air pressure equivalent to 100 mm of water is given by the hand pump.

If the pressure is maintained at 75 mm of water, the joint is assumed to be watertight.

 

 

  iv. Water test  

Provide sufficient time to set joints before the test.

Plug the lower end of the pipe and fill it with water for five days. Read initial level of water. Find water required to restore the original level after 30 minutes.

Limit: 

For small diameter: 150 ml/m of length

For large diameter: 600 ml/m of length

 

 

 

Educational Platform Under Naba Buddha Institute