Posting here for traffic - can anyone help with a boiler issue please?

[Mashandcarrots]

My combi boiler keeps dropping pressure.
We are topping it up every 3 days, the longest we managed recently was a week without needing to.

When the boiler pressure is topped up and the heating is on, the gauge goes into the number 2 zone, but almost at the end. When it’s off it goes back down to 1 but then keeps dropping, especially in cold weather, which is when we have to top it up again.

I’ve also noticed when I put the heating on, instead of the digital number going up as it’s getting hotter, it starts going down, then it’ll go up after a few minutes.

We really can’t afford too much right now, so I’m hoping whatever is wrong isn’t a major fix. Thought I’d ask on here first before paying a plumber to come out and look at it.

When I had a similar pressure issue it was the expansion vessel that needed replacing - you will need to call a plumber . And yes it willl cost .
no one here can diagnose it for you

Yeah it’s the expansion vessel thing. Mine was replaced last week and it was £210 (I’m in London and that was parts/labour)

edited to say that ours went from needing to be switched back on due to low pressure once a week to 4/5 times a day very quickly (over the course of 3days) before the plumber came

We had exactly the same pressure problem - ended up being a leak in the expansion vessel. I understand money is tight, but I really would prioritise getting it fixed, ours only got worse and pressure was going up to over 3.5. Engineer couldn't get an expansion vessel straight away and we ended up with him coming out for a few days in a row to re-adjust the system so we could run it for a short while before going dangerously right.

I’m on universal credit and I think I can get a new boiler fitted for free using a scheme from the government, so I’m thinking of possibly doing that as I can’t afford £200 at the moment or anytime soon.

Could also be a leak somewhere in your central heating system. I had this not too long ago. Only discovered the leak after 2 weeks when a stain started showing on the ceiling. Go round and check all your radiators are hot from top to bottom when the heating is on. Listen out for any strange noises....we had a chug noise for a little while before we heard the drip in the living room ceiling and then saw the stain. Homeserve insurance was a life saver as only cost £60 to get someone out to fix the leak once we found it :)

It certainly sounds like the expansion vessel however you might not need to have a new one installed. They do need to be recharged every so often, basically air is added to it with a pump (the vessel is divided in two by a diaphram with water one side and air the other: when there's insufficient air the system pressure will drop). Worth asking a Gas Safe plumber to have a look as it could be a cheaper job than expected.

Mine did this, mine was due to a leaking radiator, only noticed due to drips on a tile floor. Strangely, the leak seemed tiny compared to how quickly the pressure dropped. All fixed after a new radiator though.