ANS:D - 300 m

For large sewers, particularly those with larger diameters and greater capacities, the maximum distance between manholes may indeed be extended up to 300 meters. This spacing is often permissible in situations where conditions allow for longer intervals between access points. The decision to space manholes at greater distances is typically based on various factors such as:

1. Hydraulic Design: Large sewers are designed to accommodate higher flow rates, and their hydraulic characteristics may allow for longer intervals between manholes while still maintaining adequate flow velocities.
2. Cost Considerations: Installing manholes can be expensive, and reducing the number of manholes by increasing spacing can result in cost savings in terms of construction and maintenance.
3. Accessibility: Longer distances between manholes may be feasible in areas where the sewer alignment is relatively straight and accessible for maintenance equipment.
4. Local Regulations: Local authorities or engineering standards may specify maximum spacing requirements based on factors such as sewer diameter, flow rates, and accessibility.