Oxidation - the breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-coloured weathered surface.
Londoners are younger than anyone in the UK, London is more ethnically diverse than anyone in the UK, In London people are more educated (58%vs 38% graduates in working age population), In London people earn more money than the rest of the UK, London regards itself as innately naturally superior than anyone else despite having more in the way of things like violent crime than the rest of the country.
Older homes in older parts of Dublin would likely have more leaks. Water use is also affected by the size of gardens and lifestyle factors.