On building storm drains requiring a manhole, the manhole shall be installed within _____________ feet of the building.

The correct distance for the installation of a manhole within 15 feet of a building is guided by safety and accessibility standards. Properly locating the manhole close to the building ensures that any stormwater management can be efficiently monitored and maintained. This proximity allows for easier access for inspection and cleaning, which is crucial in preventing blockages and ensuring that the drainage system functions effectively.

Additionally, placing the manhole within this distance minimizes the likelihood of water pooling near the building's foundation, thus protecting it from potential water damage. This distance is often specified in plumbing codes to ensure compliance with safety regulations and to facilitate maintenance activities.

The other distance options are less suitable because they either increase the risk of less accessible stormwater management or may lead to potential drainage issues extending further away from the building. Therefore, the 15-foot requirement aligns with best practices for storm drain design and maintenance.