Boiler losing pressure

[TheSilveryPussycat]

Since I moved into my new house in April I've had to top up the pressure on my Baxi Platinum 28 combi a number of times. My vendor has left the pipe to do this attached, although the instructions say not to (which makes me wonder did he have this problem repeatedly and not address underlying issue).

The first time it happened I rang him to check how to top up pressure, he asked if the mains water had been interrupted (which it hadn't) and seemed to think this could be associated with it. And recently Northumbrian Water have been venting mains water to get rid of sludge (not seen any sludge in my water, though).

But... I suspect my vendor knows little, and I'm thinking it might be a leak somewhere. I will contact a professional about this but wondered if any wise MNers have any thoughts.

Yeah, usually means a leak in the system somewhere - at least that's always been the case in my experience

start by looking at the pressure release vent pipe which usually goes through the wall behind the boiler and drips or squirts onto your outside wall, leaving a wet, green or scaly mark.

Also look and feel under and around all your radiators. There might be a wet drip, or scale or a crust of mineral salts.

If the pressure gauge goes up a lot when hot and down a lot when cold, your pressure vessel needs pumping up, or possibly replacing.

An interruption to mains supply will not be relevant.

There is a short plastic pipe sticking out from the outside wall. Nothing seems to be dripping from it.

One radiator is a bit rusty at the bottom, but it could be from being scuffed when vendor fitted his own kitchen.

Resting pressure atm 1.1 Drops to .9 when I run hot water for a bit, then recovers. Goes up to 2 after a bit if I have the heating on.

Where are your pipes on each floor? I.e. plastered into wall, behind skirting, boxed, exposed surface mounted, burried in screed? We had a similar problem, eventually proving to be leaks in pipes in screed.

Get a mender in. Your pressure vessel needs attention.