Water help

[Tigs]

they are a header tank and an overflow tank. the header tank feeds the bath room cold tap and sometimes the toilet if you have 2 header tanks, its unusual but gives you 454 litres of stored water already but it may need purifying (easily done by boiling it for 5 minutes) I am guessing you only have one header tank and the overflow tank. the kitchen tap is fed directly from the mains supply.