DIY Doctor UK DIY Forums

Hi, can someone give me some advice on a pressured central heating system. We have had some work done on one of the radiators which caused low pressure on the system so i used the normal value to adjust this. Since then the pressure is continually increasing (after about 6 hours it is up to 3+ bars even with the system off). At this point i bleed a radiator to lower the pressure again. I am assuming that the valve i used to pressurize the system is faulty and need to call a plumber, but what i want to know is how dangerous is this. Would i have real problems if i didn't keep letting the pressure out. Do i need to call a plumber asap (Sunday) or wait til i have the workman back here on Tuesday - or is there anything else i can do. Any advice please.

Thanks, Sue

does the pressure rise even when the boiler is cold and inactive?

it would probably be best to avoid using the boiler until this issue has been resolved. does not necessarily need to be immediately urgent, so long as you keep an eye on the pressure and relieve it when necessary.

high pressure can expose weaknesses in the system and cause leaks. it can also damage parts of the system and possibly boiler components making for expensive repairs.

it sounds as though the filling loop is letting by - there are usually two valves on the filling loop, acting as failsafes for eachother. make sure that they are both fully closed. if the pressure continues to rise then you will need an engineer.

thanks for your advice. The pressure keeps going up even when the system is off, and goes up even more when it is on. Unfortunately with 2 children it is too cold to leave the boiler off so i will continue to keep bleeding a radiator to lower the pressure every few hours. Although i can guess what the filling loop is i wouldn't have a clue how to check whether the valves were operating correctingly.

Thanks for replying and i will definately get an engineer asap.

the filling loop - if fitted - is usually a flexible hose with a woven metal sheath. at either end will be a shut-off valve, commonly with a black handle. these should be fully closed. a quarter turn so that the handles are perpendicular to the pipework. if in line with the pipework then the valves are open. check that they are fully closed.

Thanks for all your help. The pressure is still going up but at a much slower rate (about 0.5 over night) so i think it may have been a bit of dirt stuck in the valve from where the workmen did some work on one of the radiators. I will definately try the valves on the filling loop to see if this remedies the problem
:D