No contamination of drinking water can occur if closed pipes are used for drainage of sewage. Is this always true? Explain.

No contamination of drinking water can occur if closed pipes are used

1.	No contamination of drinking water can occur if closed pipes are used for drainage of sewage. Is this always true? Explain.
Answer» No contamination of drinking water can occur if closed pipes are used for drainage of sewage. Is this always true? Explain.