Choose the Pipe and the Valve
Pipe is the first thing to consider when it comes to planning an outdoor shower. If the area temperature goes below freezing, assume that the pipe will freeze, and design the shower so the lines can be blown out or drained. Usually a combination of piping is used for an outdoor shower.
Next, decide the type of shower valve to use. Most of the time, an outdoor shower is going to have cold water running to it, so although a traditional indoor shower mixing valve can be used, this is necessary only if hot and cold water will be used in outdoor shower.