Or it could be to encourage plumbers to top up the tank by "internal"
means
so that they could get their 15 minutes of fame via a "dodgy builder"
television
programme?
Mungo

P.S. Now a proud owner of a 40Kw Worcester Bosch condensing boiler. I
know
it's the summer but on the cold mornings when the boiler kicks in it is
amazing how
fast our radiators warm up now compared to the old 24Kw boiler.