On Sat, 21 Jun 2008 22:03:57 +0100 (BST), "Dave Liquorice"
wrote:

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.

As an experiment I took one black plastic builder's bucket (3 gall
size) and filled it with 12 litres of cold water from the tap. I stuck
in my (German) Tauchsieder (1200W) and switched it on for 15 minutes.
I measured the amount of electricity consumed with my Tschibo meter at
£0.035 (3½ pence) and the temperature of the water had increased to
*beyond* hand-hot. That is, I could just about dip my fingers in, but
not for more than a second. The bucket did not deform at all. I doubt
whether another 15 minutes (when the water would be VERY hot) would
make any difference. Now I appreciate that a builder's bucket is not
the same as a loft tank, and is probably far sturdier, especially in
the rim. So what I'm looking for is either an even larger builder's
bucket, or a tank made from the same kind of material. I could, of
course, just use two (or three) builder's buckets connected together.

MM