In houses it is astonishing how many instances occur of the water of butts, cisterns, and tanks, getting contaminated by leaking of pipes and other causes, such as the passage of sewer-gas through overflow-pipes, &c.
"As there is now no doubt that typhoid-fever, cholera, and dysentery may be caused by water rendered impure by the evacuations passed in those diseases, and as simple diarrhoea seems also to be largely caused by animal organic [matter in] suspension or solution, it is evident how necessary it is to be quick-sighted in regard to the possible impurity of water from incidental causes of this kind.

Therefore all tanks and cisterns should be inspected regularly, and any accidental source of impurity must be looked out for.

Wells should be covered; a good coping put round to prevent substances being washed down; the distances from cess-pools and dung-heaps should be carefully noted; no sewer should be allowed to pass near a well.

The same precautions should be taken with springs.

In the case of rivers, we must consider if contamination can result from the discharge of fecal matters, trade refuse, &c." Now, suppose all such precautions have been disregarded.