Which surface typically would need to be grounded in a hydromassage bathtub?

In a hydromassage bathtub, electrical junction boxes must be grounded to ensure safety and compliance with the National Electrical Code (NEC). Electrical junction boxes are where electrical connections are made and, as such, they house live wires that can pose a risk of electrical shock if there is a fault or malfunction.

Grounding these junction boxes helps to protect individuals from potential electrical hazards by providing a path for fault currents to safely dissipate into the ground, thereby reducing the risk of electric shock or fire. This is critical in wet environments like bathrooms and is especially important where water and electricity are in close proximity.

The other options—plastic fittings, decorative mirrors, and wooden frames—do not typically involve electrical connections and therefore do not require grounding under the NEC guidelines. These surfaces do not carry the same risk of electrical hazards as junction boxes do, thus grounding is focused on components directly involved with electrical systems.