New boiler losing pressure

[tdm1]

We had a new boiler installed in July last year. In November it lost pressure and stopped working. So we added water, but the filling loop valve was apparently faulty, so it over-pressurised and stopped working. Expensive visit from boiler installer. On Christmas day it again lost pressure and we added water. Boiler installer said we must have a leak - not obvious anywhere, but I know leaks can be hard to track down. I've been waiting to see how long it took before the pressure dropped again. Checked pressure on Thursday - absolutely fine. Saturday morning - boiler not working because it had lost pressure. Boiler installer will no doubt say we have a leak. Which may well be possible. But - does it make sense that everything would be fine for more than a month and then the 'leak' would suddenly happen over a 36-hour period? I've lost faith in our boiler installer, so would like to be a bit more informed by mumsnet wisdom, if possible!

look for the vent pipe, which will be on the outside of your house, coming through the wall behind you boiler. Tie a plastic bag round it so that any water dripping out will fill the bad and be noticeable.

do you have any radiator pipes, unseen, under the ground floor?

feel round and under all accessible pipes and radiators for damp spots, and look carefully at all the ceilings that have pipes above.

When our boiler kept on doing this it turned out to be the vent pipe. There was also a leak in the airing cupboard, but the vent was the main culprit.

Is it under guarantee. I'd talk to the manufacturer about getting it inspected.
We'd had years of this and expensive plumbers. It was a manufacturing fault and we got a new boiler

Thank you for your responses. Unfortunately, because the boiler is in the loft, the vent pipe is really difficult to get sight of, never mind tying a bag around it!

I will go on a serious leak hunt...

We had this problem, also had a boiler in the loft. We had a British Gas Homecare engineer visit every month over the winter for a few years. The boiler would lose pressure, we would top it up and it would lose it again randomly and quickly, only over the winter months.

There were two problems, the first was a small flexible tube inside the boiler. Because it got so cold in the loft and then so hot when the boiler was on it developed a split and leaked. The leak was small and had dried up by the time an engineer came out (and the boiler had been off for a while), it was only when we got someone out quickly that it was found. We had it replaced every winter, usually after the split widened and we had had a small flood of water through the loft hatch, we kept a bowl underneath the boiler after the second winter.

The second was something to do with the thermostat which couldn’t deal with the colder temperatures in the loft. It tested as working ok, which is why it wasn’t caught for a while. British Gas eventually sent out a new engineer who didn’t just pat me on the head, but was willing to phone a more experienced member of staff who had seen it before. He recommended that we keep the boiler on low all the time because it was the influx of cold water into a freezing boiler, which then heated up quickly to very hot whic was causing the problem.

We were also told that an insulated cupboard would be helpful around the boiler, but I have no idea how true that is because we moved house! It was so frustrating, especially when the engineers would turn it off and on again, fill it and act like I was a stupid little woman when it worked. Only for us to wake up cold again the next morning.