triton t80xr leaking at botom of heat exchanger ?

hi all, I have a Triton t80 xr mains fed (not pumped) electric shower and yesterday I noticed that the shower head was pretty clogged up with lime so the overflow at the bottom of the heat exchanger started to leak and now it makes a gurgling sound, but it still seems to work and was wondering can it be fixed or do I need to replace the whole unit.
thanks