Boiler slowly losing pressure when heating turned off

I would check for leaks within the boiler, check the condition of expansion vessel (is it charged and whether it holds the pressure).

When you turn off the heating system, especially in a central heating setup, it’s common for the boiler’s pressure to drop. This is typically due to a combination of factors: 1. Cooling Water: When the heating system is turned off, the water inside the pipes and radiators begins to cool down. As it cools, it contracts, which can cause a drop in pressure. This is particularly noticeable if you have a closed-loop system with a pressure gauge. 2. Water Expansion: When the heating is on, the water inside the system heats up and expands. To accommodate this expansion, the system is pressurized when it’s initially filled or topped up. When you turn off the heat, the hot water cools down, causing it to contract, and the pressure reduces. 3. Automatic Air Bleeding: Many heating systems have automatic air vents or bleed valves that release air trapped in the system. When the heating is off, these valves may release some air, which can further contribute to a drop in pressure. To sort out this issue we advise you to monitor your boiler’s pressure regularly and, if necessary, top it up to the recommended level. Refer to your boiler’s manual for instructions on how to do this safely, or consider consulting a heating professional if you’re unsure about the process or if the pressure loss is excessive. Alex from ACB Construction Manager

Dear Chellngaz, I would suggest it"s faulty water expansion vessel.

I would check prv isn’t passing. Make sure the heat exchanger isn’t getting full of water. Make sure the expansion vessel is charged and not holding water.

Also, check pressure level