Poor households must prove their straitened means to the government , which then picks up between 25 % and 85 % of the monthly tab for up to 15 cubic metres ( 3 , 960 american gallons ) of water 貧窮家庭向政府證明他們手頭拮據(jù),政府就會(huì)為他們支付每月15立方內(nèi)用水款的25 % 85 % 。