Sanitary building sewers 6 inches or less have manholes located not more than how many feet apart?

• A. 200'
• B. 600'
• C. 800'
• D. 400'

Answer: (D)

Access to the sewer line for inspection and cleaning is provided by manholes, so the spacing between them is set to keep maintenance practical. For sanitary building sewers that are 6 inches in diameter or smaller, the line should not extend too far without an access point, otherwise locating and clearing a blockage becomes difficult and time-consuming. Keeping manholes not more than 400 feet apart strikes a balance: it provides regular access points for rodding and cleaning with standard equipment while avoiding the expense of installing too many manholes. The other distances would either add unnecessary cost (too many manholes) or make maintenance and blockage clearance awkward and inefficient (too long a run without access).