MM wrote:
I can't visualise the quantity. Is it a lot? It's 219 UK gallons, but
that is still a quantity I can't really get my head around. How much
would I use watering the garden? 20 minutes with a spray head on a
hose over approx 75 square meters, that is.

What sort of meter? A gas one? If it's an electricity meter, I wouldn't
go near it if it's wet, may be dangerous, call the electricity company.

OTOH if you mean a "metre", then just imagine it - a bit more than a
cubic yard - or a Jewson's (or someones') aggregates delivery bag full.