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

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.

There could be a small leak on one of the new joints. You may not see it, as
the water evaporates immediately on reaching the outside air. Go round with
a brillo pad (green scouring pad if plastic rather than copper) and clean
every joint well. After a few days/weeks, the leaking joint may show some
runs or staining, even if it is dry.

Also, the system may not have had inhibitor inserted when it was refilled
after the renovation. This may lead to corrosion, which produces hydrogen
that need frequent venting. This can be fixed by flushing the system and
refilling with inhibitor.

Christian.