On Sat, 21 Jun 2008 17:47:37 +0100, MM wrote:

I've made the first stage, i.e. the copper tube, about 3 metres of it
in a "snake" pattern.

Not long enough unless soldered along all its length (not spots here and
there) to some other form of collector plate a couple of square metres in
area, even then the spacing would be to high to have effcient transfer of
collected energy into the water.

Or will this plastic release toxins when containing hot water?

With your very poor collector it's not likely to get hot enough to deform,
that would be the major risk. Deformation resulting in a split or collapse
of the tank.

I can't find that Titan Wizard KM15 tank anywhere other than on the B&Q
site. It's not a Titan Tanks product as far as I can tell. You need to
find out its specified temperature range.

--
Cheers
Dave.