Italtecnica water pressure switch from Italy, 12 atm for pressure systems. Available with a swivel nut.

Inside the pressure switch, there are two springs with nuts. One large and one small.

• The large spring adjusts the pump's starting pressure. The more we tighten the nut, the more we increase this pressure. From the factory, it comes set at 1.8 bar. That is, the pressure system will start operating when the water pressure is below 1.8 bar.
• The small spring adjusts the pressure differential. That is, the difference between the pump's starting pressure and the stopping pressure. From the factory, this differential is set at 1.4 bar. That is, if our pump is set to start at 1.8 bar and the differential is 1.4 bar, then the pump will stop when the water pressure reaches 1.8 + 1.4 = 3.2 bar. The more we tighten the nut of the small spring, the more we increase the pressure differential.