Why does the pressure keep dropping on my combi boiler?
If the pressure keeps dropping on your combi boiler, it means it's losing water somewhere.
There are three common places to lose water:
1. The radiator valves
This is an easy one to check. Run your hand around your radiator valves when the heating is turned off but when there is pressure in the boiler. If any of the valves are wet, then there is your problem!
2. The expansion vessel
The easiest way to check this is to check for water discharge from the pressure relief pipe. This is usually situated outside the property and at least 0.5m below the boiler flue. It will usually be identifiable as a 15mm copper pipe. If there is any water discharging, this indicates a fault with the expansion vessel and could be the reason why the boiler pressure keeps dropping. This fault would have to be remedied by a qualified professional, as the expansion vessel is usually located inside the boiler.
3. The boiler
If there are any signs of water, or rust, from the boiler, this indicates that a component in the boiler could be leaking. This would require further investigation by a qualified professional.
If nothing is found in the above three places, then it could be a leak on your central heating system and, again, it is best checked over by a professional. Remember that anyone working on gas appliances should be 'Gas Safe Registered', so always ask to see the I.D. badge of anyone working on yours