Crikey...how long is a piece of string.........I think it all depends on how you manage it.We ourselves don't 'waste' a lot of water.Washing machine water waters the plants,some washing up water also.shorter showers,smaller toilet cysten,we even keep the 'hot ' water that isn't hot yet in bottles for the indoor plants etc etc. 13000 litres can last us on the house alone about 3-4 months.Bring a pool into the equation and all this goes out of the window.