Vokera Compact Dirty Hot Water ?

Vokera Compact

When the hot water tap is turned on dirty water comes out, then sort of clears after a while but is still a little murky, at the same time the pressure in the CH drops. I removed the Heat Exchanger and when I blow through it from the cold water inlet air comes out at the CH side. Just wondering if, before I go and buy a HE it could be anything else.

Any help greatly appreciated.

nope nothing else, its your heat ex

Thanks for reply, thought so