On Thu, 01 Apr 2010 12:20:06 +0100, Ed wrote:

I don't know what KISS stuff is

Keep It Simple, Stupid.

but I have just tried the siphon method as you described and it works
brilliantly. WOW!!

Simple and effective, the water level in the two butts will remain
the same no matter which you draw off from. Obviously with B being a
foot lower than A, A won't be full. Simple to solve as you've already
said with some breeze blocks. Remember a decent sized water butt full
of water will be quite heavy, something between a 1/4 and 1/2 a tonne
depending on size. (60cm dia 1.3m high butt is over 1/3 tonne).

--
Cheers
Dave.