In article , Marcus Fox wrote:

In the UK, building regulations state a floor loading of no greater than 1.5
kN/sq m

snip

If you have a limit of 1500 N, you can have a maximum of (1500/9.807) 152.95
litres for every square metre of tank base area.

The math does not work that way. The floor loading of 1.5 kN/sqm is a
design guideline for the static load of the whole floor. You can if
you wish put more of that load in one area then in another. Consider a
person carrying another. Given a generous footprint of 30cm X 30cm
according to the 1.5kN/sqm figure those two people can weight no more
then 135N == 14kg == 30lbs! Even one person is bigger then that.

At the same time the loading figure does not allow you to put the
whole load of a large room on a small footprint.

The 1.5 kN/sqm loading figure is a magical design number which assumes
an evenly distributed load to make the math easier.