Having worked long for and retired from a domestic water purveyor, I can understand the concerns that a significant leak and loss of water pressure can have on health concerns.
Leaks on back-yard or cross-country pipes (as opposed to under paved streets) can be difficult to locate. If there are significant sand or gravel in the underground terrain, the leaking water can surface a distance from the actual leak.
A break in a pipe might actually suck in water or other pollutants outside the pipe into the distribution system. This is why there are requirements to separate sewage lines from domestic water supplies. Separation by placing the sewer lines deeper or concrete encasement or long joint-less segments of one or both pipes.
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