Dropping pressure on Ariston Combi boiler

As I cannot see my original post on this I will try again. I had an Ariston Genus HE 30 installed six months ago and have a problem with the pressure dropping. after installation I had to top up about every 4 to 5 weeks, but over the months it has progressed to topping up every 7 to 10 days now as the boiler drops about .1 a day. I have had the engineers in and we have checked all the rads for leaks and air locks. We could find no visible signs of a water leak anywhere and as the pipes are all drops and not under concrete that much water leak over that period would show on the ceiling I would have thought. The engineer thought that perhaps there was a hairline crack in the condenser thingy ( cant remember the name) but cant see any signs of staining. There is no dripping or staining on the outside little overflow pipe. He has gone away and is going to consult with the Ariston people to try to get some suggestions, so I thought maybe someone has had the same problem and could help

Bob

When rads ar totally cold remove the plastic tops from rad valves & feel spindle for dampness it is most likely that a few (or most) rad valves are weeping & when hot moisture evaporates. It is unlikely to be main heat exchanger on a 6 month old boiler even if it is italian

There is one rad that does have a very small drop of water when its cold but surely with the pressure drop of .1 which is possibly a half a cup of water , surely it would be a lot more than a couple of drips.

try your expansion vessel , it may be faulty , get a car pump with a gauge on and make sure its charged to 1 bar

prv

expansion vessel it not in it a problem, is necessary,
1. To merge water from a copper
2. To pump up air in a broad tank, nearby 1 Bar of pressure.

But a problem, I think that it is necessary to solve so. There are three causes of defect of your copper.
1)Water leaves heating system back in waterpipe system, through ïîäïèòî÷íûé a tap.
2)The Faulty heat exchanger for hot waters.
3)Leak of water from heating system through.