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Wiring Bathrooms

Bathroom electrical work raises some special considerations, beyond even those of the kitchen. Both have water around, but bathrooms are enclosed, usually smaller, and often put moisture into the entire air space of the bathroom. That makes wiring them for safety all the harder and more important.

Some electrical codes take these facts into account differently than others. But common sense and good wiring practice alone are enough to guide the do-it-yourselfer in this area.

A vent and fan isn't always legally required. But it very often makes the most sense. Windows, when they exist in a bathroom, often remain closed during showering, as does the entrance door. The build up of hot, moist air creates several potential problems.

Water itself is a decent insulator, contrary to popular belief. What makes it a good conductor - and therefore potentially dangerous around electricity - is the fact that it's almost never pure. Minerals and salts that dissolve readily in water are everywhere in the bath. Sweat from feet and hands, calcium carbonate, iron oxide and more all turn water into a good conductor.

That means that plugging in a hair dryer, turning on an electrical heater and other common bathroom devices raise the risk of shock, unless outlets and devices are wired properly. When they are, the risk is no greater than it is in the kitchen or elsewhere that water and electricity are likely to mix.

GFCI (Ground Fault Circuit Interrupter) receptacles are one of the most common ways to deal with that problem in the case of outlets. They are designed to instantly cut off the juice whenever the current or voltage exceeds the design limit. They work. A 4-watt nightlight is plugged into an outlet that is incorrectly delivering 150 volts. Turn on the switch and, boom, the GFCI circuit trips. Press the center button to reset and it will blow again.

But there are more basic considerations.

Isolating devices onto separate circuits increases the margin of safety in the bathroom. Having an under-the-sink hot water device on a different circuit from the main light switch is one example. Wiring the electrical heater in the wall to a different circuit than the vent/fan is another. Having strip lights over the mirror on a separate circuit from the main ceiling light is yet a third.

When designing or re-doing the wiring system for the bathroom take into account the average loads of all expected devices. Install circuit breakers to match. In most cases 20-amp breakers are the usual choice. By designing safety features in depth, with redundancy, you provide that extra margin of safety. That can mean the difference between injury or fire and a relaxing time in the bathroom.