Today I’m sharing the answer to the question – why is my boiler losing pressure? Which I learnt the hard way. If you read my blog regularly, you’ll know that I’ve been flipping my fixer-upper house since late 2019. One of the first things I did when I began, was get a new boiler installed. This worked perfectly for a few years, but in 2023, my boiler started losing pressure. Keep reading to find out what happened next.
Why is my Boiler Losing Pressure? – Stage One
The engineer who installed my new combi boiler had annoyingly gone out of business by the time my the issue of my boiler losing pressure began, so I got someone else out to look at it. They suggested the boiler was faulty, and to contact the manufacturer. I felt like this was a stretch, as it was so new, so I got a second opinion. They too said the same, so I contacted the manufacturer – Baxi.
A Baxi engineer came out, and he said there was a leak on one of my pipes. He assured me the boiler was absolutely fine, and said I needed to get someone to find the leak. For context, I live in a 1950s semi in Manchester – The walls are mostly original plaster, with the pipes buried deep. So aside from checking around radiators – which all looked ok, I couldn’t find any signs of a leak, or look for them, without lifting floors and smashing walls.
Why is my Baxi Boiler Losing Pressure? – Stage Two
Over the next two years, I had 3 different engineers out to try to find the leak, without success. We lifted floor boards upstairs and checked the visible pipes on the landing and in the bedrooms, with no leak being found. The system was drained and flushed, in the hope it would show the leak so we could find and fix it. This didn’t work either. Short of smashing out walls in every room to check buried pipes, there wasn’t much else they could do.
In the end, I was advised to watch and wait. To begin with, the boiler pressure would drop maybe once a week in Winter and once a month in Summer. I’d top the boiler up, and things would carry on until next time. By December 2024, I was topping the boiler up every two to three days, so I knew the issue was getting worse, and things would likely happen soon.
My Ceiling Came Crashing Down – Stage Three
In March 2025, the kitchen ceiling collapsed directly below the boiler. (The boiler is located inside the airing cupboard in the first floor bathroom). Only once the ceiling was down could we see there was a tiny leak in the hot water pipe, at the first corner joint after the hot water exits the boiler.
This tiny drip was the source of the pressure issues all along. It had been dripping directly onto the original 1950s kitchen ceiling, which had been overboard with plywood and painted in gloss paint at some point many years ago. Due to this, the typical paintwork staining you usually get with leaks didn’t happen.
How to Stop my Combi Boiler Losing Pressure – Stage Four
The engineer came out and the plastic joint that was leaking was replaced. Thankfully, the boiler pressure became stable, and I thought that was the end of it. Sadly for me, my kitchen ceiling sprung another leak on the other side of the room in September 2025, and the boiler pressure dropped again. This time it was the other end of the pipe that had leaked previously. This too was fixed, and the engineer then checked and re-sealed every visible and accessible area of pipework.
Thankfully my boiler pressure has remained stable since then, but the entire process was a nightmare. The engineer blamed it on cheap plastic fittings being used on the pipework when the boiler was moved upstairs in 2008.
So while all of the initial symptoms pointed to it being a boiler fault which was causing my boiler to lose pressure, it was actually a leaky pipe causing my boiler to malfunction.
How to Top up Boiler Pressure
When it comes to topping up boiler pressure, I want to start by saying I am not an expert. The best thing to do is check your individual boiler’s user guide for instructions. Alternatively, when you have an engineer out to look at your boiler, ask them how to top up boiler pressure on your boiler, in case it happens again. It’s very important to NEVER top up your boiler too much. My Baxi combi boiler has a clear indicator which shows the “green zone” – You should aim to top up the pressure so the needle is in the middle of that gauge, ideally. I found this video really helpful when I needed a refresher.
So there you have it! My boiler losing pressure caused chaos over three winters. I am looking forward to knowing I’ll wake up in a warm home every morning this Winter! Let me know in the comments if you’ve had any issues with your boiler losing pressure.
