What if...

[Nix]

Thanks NR, you're quite right, I was aware of pumpless circulation where the heated liquid would rise and cold drop creating a circulation but never seen one! My mistake, should've thought more before posting but it does bring up a very interesting scenario where perhaps someone would want to make a pumped system pumpless - interesting! It would have to not have the intense heat that a modern gas boiler is capable of (hence the need for a pump) but perhaps a slower less intense set up?

You've got me thinking...