8.4M US gal/year * 3.785 US gal/litre / (365 24 60 * 60) = 1 litre per second.
Put another way, if the average US household uses 138 US gal/day [0] then this is 8.4M / 365 / 138 = 168 average households.
[0] https://en.wikipedia.org/wiki/Residential_water_use_in_the_U...
8.4M US gal/year * 3.785 US gal/litre / (365 24 60 * 60) = 1 litre per second.
Put another way, if the average US household uses 138 US gal/day [0] then this is 8.4M / 365 / 138 = 168 average households.
[0] https://en.wikipedia.org/wiki/Residential_water_use_in_the_U...