The 28mm Excess Flow Valves fit at the domestic side of the gas meter.

In the event of a break in the supply such as ruptured pipes, appliance thefts (such as boilers), the Magne-Flo valve detects the excess flow of gas. Its unique magnetic ferrite construction is designed to cut in whenever the normal flow is breached, preventing the rapid build up of potentially lethal gas.

After repair, and normalising of gas pressure, the valve resets itself and is ready to check for further leaks.