Jonathan George wrote:

The basin and bath both have mixer taps (monobloc for the basin), and
all cold water is fed from the rising main. Apparently this is against
building regs or something similar, as there are no double check
valves or similar. Is this correct?

That depends. Many mixer taps do not actually "mix" as such - they
squirt the water from each supply out of different (often concentric)
spouts such that the mixing happens after the tap. If yours are like
this, there there is no problem.

I've got a cold water cistern in the loft and a hot water tank in the
airing cupboard, next to the bathroom. Assuming the previous paragraph
is correct on the cold water front, I was planning on taking a branch
from the cold water feed to the hot water tank and using this to
supply cold water to the bath and basin taps, leaving the toilet on

If you have taps that mix internally (as some of the older designed did)
then it is probably going to be much simpler to install a double check
valve on the cold pipe feeding each tap. These are not unlike a straight
compression fitting (bit longer) and are fitted in exactly the same way
- chop a bit out a pipe and stick it in. (Not sure why, but some folks
seem to think there is some big mystery to double check valves)

the rising main. The shower installation instructions say that I
should have a separate 15mm feed from the cold water cistern to the
shower, and a 15mm feed from the hot water tank taken off below the
join to the vent pipe and before any other draws. All sound ok?

Yup - you should install the dedicated cold feed for the shower so that
it is sighted a little lower in the cold cistern than the feed that goes
to the hot water cylinder. That way if the cistern gets drained it is
the hot water that stops flowing first!

easier said than done, as they are right against the wall, I can use
standard 32mm and 40mm pushfit connectors to join them onto new
plastic pipes and then use solvent weld/more pushfit depending on how
confident I'm feeling. Does this sound ok? And if so, is it necessary
to strip the paint off the old wastes before I do it?

You may find this joint is better made with a plastic waste compression
fitting rather than push fit, since the matching of the exact diameter
is slightly less critical.

What's the best way to strip old paint off pipework, especially if
access is limited (why anyone would paint pipework that's right at the
back of the airing cupboard, I have no idea).

Heat with a blow torch, then wire wool.


--
Cheers,

John.

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