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Heating

Boiler losing pressure but no leaks from radiators and no drips from pressure relief valve?

Anonymous user 21/11/2025 - 11:04 AM

We recently upgraded our home and installed a new boiler and central heating system but we're running into an issue with the boiler losing pressure. Once it's pressurized to about 1.5 bar, it works perfectly fine while it's on. But when the thermostat turns off, the pressure drops again. We've had the boiler inspected and there’s no unwanted water in it and no leaks from the pressure release outlet. This is happening really often and sometimes the boiler shows 0 bar until we repressurize it. I've checked all the radiator valves and visible pipes, and I can't find any obvious leaks. There aren’t any pipes beneath the main floor either and there are no damp spots on the ceilings. Any advice would be greatly appreciated!

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3 Answers

Kanata Development Inc.

Rating: 5 out of 5

Keswick, Ontario

Even though there could be multiple reasons but Most common cause is air in the system. Its recommended to have an expert to inspect it for trapped air , undersized expansion , faulty pressure relief or it could be the system is settling meaning slowly getting rid of the trapped air .

Answered8 October 2025

ProLogic Comfort Solutions

Rating: 4.9 out of 5

Mount Hope, Ontario

Most all boiler systems are closed loop systems. Over time as the entrapped air finds its way out through bleeding or auto air vents the pressure will drop until all air is gone unless the system has an auto fill installed. I would suggest having a boiler technician from a different company access the installation and see if they have any recommendation on the installation as there is a lot of good companies installing boilers but there is an equal amount that have much to learn about it.

Answered27 October 2025

Omega Heating & Air Inc.

Rating: 4.8 out of 5

Mississauga

After installing a new system you could possibly still have some air pockets throughout the system and they require to be bleed out completely. If you are losing pressure consistently then it sounds like you may have some other possible issues. Happy to discuss and help if required. Thanks Omega Heating & Air Inc

Answered21 November 2025