Central heating dropping to 0 pressure every time heating goes off- no obvious sign ofleak
Anonymous user 14/03/2024 - 2.37 PM
We have a fairly newly installed (year ago) pressurised system (kept original boiler as was only a few years old). We have had minor issues with losing pressure but discovered a small leak close to the boiler. However, two nights ago, my partner heard 'rushing' water coming through the pipes and jumped out of bed expecting to go and find a pool of water somewhere but there was nothing to be found but pressure was at 0. A heating engineer came and put rad seal in to the system to resolve any 'leaks' and told us to keep the heating on for a period of time to let it circulate. We did so and then let it go back to its usual schedule. The pressure remained constant when heating was on and I checked it periodically. When the heating had gone off, I checked the pressure and within less than an hour of it going off, the pressure was at 0. We kept the heating off and even with the heating off and the pressure at 0, my partner, again, heard the water running down through the pipes. We have now done this twice more and pressure just drops when the heating goes off and we can hear water pouring through the pipes...Does this sound like a leak or an issue with something else e.g. expansion tank/ valve etc?
Are you a tradesperson and able to answer this question?
This can be fairly straightforward to rectify. Obvious starting point is how big the property is and what boiler was installed. If there’s not enough expansion available this can cause pressure issues. A common problem in the industry is boilers will be replaced but the system is forgotten about and numerous installs should have had an extra expansion vessel fitted.
The next check is if the expansion vessel has the right charge in it. If the vessel is flat this can cause the pressure to rise too much and allow the prv to operate, same way not having the right expansion will result in the prv operating and losing all pressure.
Leak sealer will only work if there is a leak and it’s exposed to air to allow it to seal.
You’ll need a decent engineer out to check the system over and the vessel in the boiler to see if these are ok, and have the boiler repaired under the warranty, especially if it’s only a year old.
Answered15 January 2024
3
Anonymous user
Check the external PRV for discharge, sounds like the boiler over pressured and discharged and got stuck open. Does the boiler still sit at 0 bar when it’s topped up?
Hello Spanna_23,
The symptoms you've described, especially the pressure dropping when the heating goes off and the sound of water running through the pipes, could indicate a leak or an issue with the expansion tank or pressure relief valve. It's advisable to have a heating engineer or plumber inspect the system thoroughly. They can perform a pressure test, check for leaks, and examine components like the expansion tank and pressure relief valve to identify and address the root cause of the pressure loss. Addressing the issue promptly will help prevent further damage and maintain the efficiency of your pressurized heating system.
If you have pressurised an old system then this can cause water leak issue with the joints of the pipes. If you have added radiators to the system you will need the correct size of expansion vessel to cope with the volumn of water. Also check the safety pipe to outside from the pressure relief valve ( PRV ) to see if it is leaking and this could be related to the expansion vessel not having enough air pressure inside. This could be an external or internal expansion vessel and if it is the latter then you maybe able to contact the manufacturer's depending on the length of your warranty to changed it at no cost.
Hi, it’s sound like potentially a faulty expansion vessel but this could be also a number of other things, I’d recommend getting a gas engineer round as in my personal opinion 9 times out of 10 putting rad seal in isnt the fix too the issue, hope this helps,
Kind regards
