The power to the system must be turned off before starting to re-pressurise the boiler. It’s something the homeowner can do themselves but if the pressure continues to drop then a heating engineer will be required. Modern boilers work best usually around 1.5 bar. The boiler will have a pressure gauge that shows the minimum and maximum operating pressure.
There are 3 main reasons why the pressure could drop.
Bleeding Radiators Low Pressure
When bleeding radiators air is being let out of the system and can cause the pressure to drop. This can be easily rectified by letting more cold water back into the system. This is simple to do however each boiler is different so you will need to refer back to the boiler manual or the manufacturer’s website for direction.
If there is a leak in the system the pressure will continue to drop even if you have added more cold water into the system. It can be very hard to locate a leak but the best place to check first is the radiator valves. Wipe the valves with kitchen roll and place a tray beneath it to collect any dripping water. If you are unable to locate the leak then an engineer may be needed to locate and fix it because the leak could be behind a bath panel or floorboard.
It is important to have your boiler serviced annually as this helps to keep your boiler running efficiently. Any fault will be detected earlier and can be fixed before further problems develop. If the pressure in the system keeps dropping after cold water has been added, it could be the expansion valve that has failed or limescale could have built up in the boiler. A certified engineer will be needed to check this out.
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