Hi

We have a modern house (4 years old) with an unvented HW & CH system.
A Vaillant boiler with integral circulation pump, a pressurised hot
water cylinder, a small expansion vessel above it and lots of pressure
valves!

Three seperate questions:

1) We get a lot of air in the Hot Water, in comes out the tap looking
white because it is full of tiny air bubbles. Not a major probblem in
it's self, but is it telling us something else needs fixing? Can it
be fixed?

2) Upstairs Water Pressure Issues. The upstairs mains cold water
seems to be also regulated by a pressure valve - this seems to be a 3
way preasure valve, taking mains water in and feeding (max 6 bar?)
cold water to both the ho****er cylinder and the upstairs cold taps.
The issue is that when filling the bath, if you turn both Hot & cold
taps on, the resulting pressure is substantially less than only having
hot on or only having cold on, what is going on? Why does the cold
water need regulating in the first place (just to balance it?) and is
something not working right?

3) Rads in the loft. We are having a shell loft conversion completed
and intend to extend the current CH system into the loft. Are there
any issues with having rads higher than the expansion vessel in the
closed 2.5bar ish CH system? If this does cause issues can I just
raise the pressure vessel?

Thanks in advance.
Kev