All 125-volt receptacles located within how many feet from the inside walls of a permanently installed pool require GFCI protection?

The requirement for GFCI (Ground Fault Circuit Interrupter) protection for 125-volt receptacles is based on the electrical code's safety standards, particularly in locations with a higher risk of electric shock, such as those near swimming pools. The correct distance of 20 feet is established to ensure that any receptacles within that range are adequately protected from possible electrical hazards due to water.

In the context of a permanently installed pool, the 20-foot distance is crucial because it encompasses areas where people may be in or around water, thus increasing the likelihood of direct contact with electricity. GFCIs are designed to quickly cut off electrical current in the case of a ground fault, significantly mitigating the risk of electric shock in such environments.

By adhering to the 20-foot requirement, it ensures that any receptacle within this boundary is equipped with GFCI protection, thus promoting safety standards that prevent accidents. The other distances listed do not meet the established guidelines that provide the necessary safety margin in relation to the proximity to the pool, leading to increased risk if those receptacles were not GFCI protected.