Last March I had my old back boiler replaced with a combi boiler. I think I remember having to top up the water after a couple of weeks by 1/3 of a bar or so. I then kept an eye on it throughout the summer and the pressure never dropped so I thought all was well, until yesterday when I realised a couple of the radiators needed bleeding. After bleeding them the pressure had dropped at least 1/2 a bar. Is this normal over a period of around seven months? Does a new system need topping up after a while anyway? There are no signs of leakage.
TIA
TIA