Safety Valve to water heater. 3/4 Inches. Designed for pressure between 6.5 to 8 Bars. This is a valve mounted on the pipe for supplying cold water into the boiler. When the heater is gaining maximum water volume, the valve does not allow water to flow in the opposite direction. Safety valve designed to protect the boiler from the pressure arising during heating of water changes so as to reset the excessive volume.