A Pressure Pump is installed on the outlet of your tank.  This type of pump is primed and ready to use at all times.

When you turn on a tap, hose or sprinkler, the pressure switch senses a drop in pressure, and turns the pump on.  You will need an external power point next to the pump, turned on at all times.

These pumps of different brands sell for between $500 – $600

Below is a Pressure Pump, connected to a tank, then to an automatic sprinkler system.

Tank with Pressure Pump.