In a low water pressure area, why would water from a shower take several seconds to flow after the shower is turned on?
As requested:
Is this low pressure system for your shower part of a tub also? If the water is being diverted up to a shower head it may take that long to fill the pipe, turn the pressure off the pipe is still full so it flows when turned on. Other than that we would need to know more about the controls on the pump.