central heating pressure holds for 3 months then loses pressure
Anonymous user 28/02/2024 - 3.29 PM
Since I've moved into this flat I have had a problem with my central heating. I have had numerous engineers out to the house who have tested the system, had the floorboards up, and most recently, run sealant through the pipes.
On two occasions now, after an engineer has been to the house, the pressure has managed to hold for about 3 months. All has been well. Then, when the pressure has fallen down to zero, and I have topped it back up to the requisite position, it has fallen rapidly (i.e. within the space of a week/couple of weeks).
I am beginning to think that the falling pressure is something to do with how I am topping the tank up - as it is inexplicable the system holds for 3 months at a time when the gas engineer does it, and then fails when I do it.
I have plastic pipes and various engineers have told me that this is the problem - although I cannot afford to replace to the whole system in order to rectify this.
- I have a condenser boiler (Worcester Bosch) which was installed about 6 months ago. I don't understand how this can be a leak in the system if the pressure is capable of holding for 3 months.
- Hi again - thanks - it is not a combi boiler - it is a conventional system
Are you a tradesperson and able to answer this question?
Hi, your boiler is known as a sealed system. In the event of over pressure there is a safety relief valve connected to a copper pipe that runs outside from the boiler.
A quick check when the system next runs dry is to see if there is any water present in this pipe; if so, the pressure relief valve could be lifting and then not re-seating correctly. If the boiler is only 6 months old that would be covered under the warranty.
This is how I determine the source of a leak on your sealed/pressurised heating circuit/boiler.
First electrically isolate the boiler by turning it off at the nearby fuse spur switch. Increase the system pressure to 2 Bar no more!. Then isolate the flow & return heating pipework by turning off the two service valves underneath the boiler.
Then leave the boiler preferably over night and look at the pressure gauge to see if it has dropped, if not then we can eliminate any internal leaks within the boiler i.e. cracked heat exchanger or passing PRV, then open both of the service valves on the flow & return pipes, if you notice a small pressure drop after turning them back on we can safely assume that the leak(s) are on the heating circuit pipework.
As you have not stated what type of boiler you have, i.e. a Combi then the heating water is escaping somewhere on the heating circuit but if you have a Conventional/System boiler please let us know so we can advise you further.
NB: Remember to bring the pressure back down to 1 Bar if no pressure drop occurs during this exercise before turning your boiler back on by simply opening a radiator air bleed plug and catching the water in a suitable container, may have to repeat the process several times!
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Update:
Thanks for the additional information. Know I now that you have a Conventional boiler the plot thickens. One cause but not necessarily the root cause of the pressure loss could be your heat exchanger inside your hot water cylinder, if it has become perforated/ruptured heating water could escape in to your domestic hot water cylinder and the most common sign of this is discoloration of your hot water. But you have not responded regarding my initial fault finding comments as in the first paragraph above, this exercise needs to be carried out first by a competent heating engineer before you move on to my latest possible fault scenario!
Unfortunately I can no longer offer any more help
on this matter as I am taking a well earned rest, but good luck with locating the problem unless someone else want's to jump in a take over if you are still continuing to have issues.
