I think weekly, and the number of cubic metres you get at each price point should depend on the number of identification cards registered at your address.

If we use a model rate of $3 per cubic metre as a baseline, and you, your spouse, and two children all consume the average amount of water per day (225 L), the household would consume 6.3 m³ of water per week. You would be billed $3 per m³ for the first 4 m³. Then you would be billed $6 per m² for the next 2.3 m³. This totals $25.80 for the week.

If we consider a two-person household, just you and your spouse, water usage would be 3.15 m³ for the week and you would be billed $3 per m³ for the first 2 m³ and $6 per m³ for the last 1.15 m³. That totals $12.90 per week.

Under the current system, you would be billed $4.287 per m³ which comes out to $27.00 for the 4-person household and $13.50 for the two-person household per week, so my system results in roughly the same water bill for average consumers.

On the other hand, if you're a Hollywood actor living in a mansion with your spouse and each using 5 times the average water usage in order to water a huge garden and run a water fountain, your water usage would be 15.75 m³ per week, for which you would be billed $1,434 for that week.

If you use another 12 m³ to top up your swimming pool because the Kardashians or some other trashy celebrities are coming over for a party hosted at your mansion, your water bill for using 27.75 m³ that week would shoot up to $92,147.

In comparison, even if you are being penalised by the Department of Water and Power for excessive usage today, you're still only charged a maximum of $5.414 per m³, so that actor would be charged only $85.27 at most for the normal week and $150.24 for the pool week.