Degradation of water quality
Entry of subsoil or contaminated water through leaky pipes and joints especially in intermittent system may cause the degradation of water quality in the water distribution system. At the dead ends of the system accumulated solids may aid the biological organisms, which will affect the water quality with reference to taste and odour.

Prevention of Water quality Degradation
In order to prevent water quality degradation the water main should be laid, with at least 3 m of separation horizontally, from any existing or proposed drain or sewer. If local conditions prevent this lateral separation, a water main may be laid closer to a storm or sanitary sewer, provided that the main is laid in a separate trench, in such a way that the bottom of the water main is 50 cm above the top of the sewer.

In situations where water main has to cross house sewer, storm drain or sanitary sewer, it should be laid at such an elevation that the bottom of the water main is 50 cm above the top of the sewer with joints as remote as possible. This vertical separation should be maintained for a distance of 3 m on both sides, measured normal to the alignment of sewer. Where the conditions prevent the minimum vertical separation set forth above from being maintained, or when it is absolutely necessary for the water main to pass under a sewer, the water main should be laid with flanged joints for a length of 3m on either side of the sewer. However, a vertical separation of 50 cm, between the water main and the sewer should be maintained.
Regular leak detection and rectification of the leakages in the system will prevent the water quality degradation.