Pressure regulator attaches to outside tap. It reduces the pressure of the water to 20 PSI (1.5 bar), this ensures that the micro irrigation system is not over pressurised, and that performance is optimised. There is an integral filter to prevent dirty water affecting dripper performance. Inlet is 3/4" BSP this screws directly onto a water computer, or most outside taps. Supplied with two outlet adaptors : 4mm and 13mm.