This was the project to whip out the house boiler and put in a new one that would heat both the house and the pond. A huge learning curve that I didn't fully understand until the day the plumber came. And the plumbers mate who came to soak in the enormous novelty factor of 'the job'. Needless to say, it all went swimmingly well and worked first time - and still works, touch wood. Thanks also to Mickosan who helped me understand it. Plumbers were Knowles of york with bits from Koi Polloi.