Boilers
Boiler Expansion Vessel
Internal tank with a nitrogen-pressurized diaphragm that absorbs water volume expansion as the heating circuit warms up.
What is Boiler Expansion Vessel?
As water heats up inside a sealed central heating loop, it expands. The expansion vessel absorbs this extra volume so boiler pressure remains stable between 1.2 and 2 bar instead of spiking past 3 bar.
When you encounter it in an emergency & typical cost
If your boiler pressure shoots up to 3 bar and drips from the pressure relief valve whenever heating is on, the expansion vessel needs recharging or replacement.
Arrival within 20-35 minutes