.....in the water, that is.

Two problems:

(1) When I run the cold mains at full blast (e.g. the bath tap) I get a
few black flecks in the water. Not a massive amount, but I didn't think I
should get any.

(2) When I take the head off the electric shower and run it full blast on
cold, a large amount of cr*p comes out. This seems to be mainly limescale,
black on one side, but there are also some coppery blue bits. I expect the
very old Triton T80 shower to have some clag in as this is a very hard
water area, but it just seems to keep on coming. I thought the shower has
a fairly small area of heating coil and there seems to be an awful lot of
stuff coming out.

We should be getting rid of the shower soon - new heating system which
will run a mains pressure shower - so I'm not too worried about that. I'm
more concerned about the black bits in the cold mains.

If this is from internal pipework this isn't too bad as this is also going
- ripping it all out back to the stopcock (and changing the stopcock
because it doesn't stop).

If it coming in from the mains water supply I would prefer that it did not.

Is there any easy way to filter incoming cold mains without drastically
reducing the pressure?
I presume the filter should be easily changeable as well.

TIA

Dave R