You probably have a jet pump that is either set up normally ( two pipes that connect to the pump housing from the cistern and one other one feeding the system)or it may be a jet pump set up for a shallow well configuration (Only one pipe from the cistern and one pipe feeding the system). In either case you should have a pressure switch at the pump and sometimes even attached directly to the pump. Around here the most commonly seen brand is the “Square D” brand. Turn off the power to the pump and take the cover off the pressure switch. There should be two screws with springs around them. These adjust the pressure. Look underneath the switch cover because sometimes they print setting information there.With square D switches and several other brands there is a tall screw and a short screw. The nut on the tall screw is turned clockwise to adjust both the cut-in and cut-out pressure simultaneously. The shorter screw is used to increase or decrease the cut-out pressure only.The normal setting for most pump systems is 30-50 and this seems to work for most domestic systems. After you have tightened the screw a couple of turns,replace the cover and turn the power back on. You may have to bleed off some pressure to get the pump to start again so you can note at what pressure the pump kicks off at. Bleed again to note where the pump kicks on again. You may have to go back an adjust it a little more and then recheck the pressures again till you reach 30-50 lbs. Hope this is of some help!