Been down that road myself more times than I care to admit. Boilers are sneaky like that—one day they're fine, next day you're topping up pressure every few hours. Agree that checking simple stuff first is key, but honestly, sometimes it's the weirdest things causing trouble.
Once had a similar issue, spent days checking joints, fittings, valves...everything obvious. Turned out the expansion vessel had lost its charge and was causing pressure fluctuations. Took me forever to realize because I was so focused on finding leaks. A quick recharge sorted it instantly. Another time, it was the tiny automatic air vent at the top of the boiler slowly letting air in and pressure out. Those tiny vents are easy to overlook.
These days, whenever I see random pressure drops without visible leaks, expansion vessel and air vents are the first things I check. Saves me a lot of headaches.
Glad you got yours sorted though—always feels good when you finally track it down.
"Turned out the expansion vessel had lost its charge and was causing pressure fluctuations."
Yeah, expansion vessels are sneaky culprits for sure. Another thing I've seen a lot is the pressure relief valve dripping just enough to drop pressure slowly—easy to miss if you're not checking the discharge pipe regularly. Had one customer convinced they had a hidden leak under the floorboards...turned out it was just that valve quietly dripping away outside. Boilers definitely keep you on your toes. Glad you got yours sorted though.
Expansion vessels and PRVs are definitely common culprits, but another sneaky issue I've run into is air trapped in the system. Sometimes bleeding radiators isn't enough—air pockets can hide in pipework loops or higher points. If you notice uneven heating or weird gurgling noises, try shutting off all radiators except one at a time, then run the boiler briefly to push air out systematically. Bit tedious, but it works wonders...saved me from unnecessary part replacements more than once. Boilers love keeping us guessing, huh?
Totally relate to your air-pocket woes. Had a boiler once that drove me nuts with random cold spots and weird noises. Tried bleeding radiators repeatedly—no luck. Turns out, exactly like you said, air was hiding in the pipework itself. I ended up doing something similar, isolating sections bit by bit and carefully running the boiler. Took ages, but finally got it sorted. Boilers really do seem designed to test our patience... Glad you figured yours out though, feels great when you finally crack the puzzle.
Had a similar issue with my boiler setup last winter—air pockets can be sneaky little things. Took me forever isolating each radiator and pipe section, but got there eventually. One thing I noticed though: after all that tinkering, the pressure gauge started fluctuating more than usual. Did anyone else experience pressure inconsistencies after sorting out air issues, or was that just my luck...? Curious if there's a safer way to avoid messing up the system pressure while chasing air bubbles around.
