I have a Vokera 'Minute 20SE' boiler. After recently having a Megaflow
mains pressure hot water tank fitted and some additional radiators, I
have noticed that the pressure in the system needs topping up from the
filling loop every 3 weeks or so. Before I had the Megaflow and rads
fitted, I only topped up approx 2 or 3 times a year.

As well as the pressure falling, some of the upstairs radiators
require bleeding every few weeks too. (I bleed them after topping up
the pressure in the system.)

Please can anyone suggest why these things are happening, and what I
can do to fix them? I don't want to keep injecting oxygenated water
into the system, and the water must be going somewhere!

Is it significant that the plumbers fitted an 'automatic air valve' to
the pipework beside the Megaflow? Could this be the cause? (How should
the small finger screw be set on these valves, by the way?)

As a precaution, I have arranged for a Vokera engineer to take a look
at the boiler next week. Could a safety valve could be leaking enough
to cause these problems?

Any ideas very welcome.

David Green