In our area potable water is found mixed with dirty sewer. The reason is the parallel placement of both the lines. Also the joints of the water lines are found leaking. After persuading the authorities, pipe lengths were removed from the joints and new pieces of 4 inch pipes provided that gave some relief.

Old joints were having cotton sutli wrapped which is worn after a few years. Poor maintanance of parallel sewer lines forces dirty sewer water into  the porous joints of the drinking water supply when there is no water supply. The present technique seems better in which rubber gasket is tightly fitted in joints.

My questions are:

 (1) What should be the vertical and horizontal distance between sewer and water lines?

 (2) Is there  any latest technique to detect the position of leaking joints?

 (3) Since old cast iron  pipe lines are not the cause of mixing, the problem is with the joints only. Kindly suggest methods to repair and seal the leakage.

Jarnail Singh
jsbhatia55@rediffmail.com