The reason most RV shower heads leak is because the pressure fitting between the pipe and the shower head itself is plastic. Your shower head at home doesn't really leak because metals are often much better for the pressures that occur when you turn on the shower. One of the best ways to fix a leaky shower head is to remove it, make sure it is clean and then wrap the threads of the pipe with teflon tape. This creates a better seal and often will stop the annoying leaks you can experience in your RV shower.