Question for National Water & Sewerage Corporation (Head Office)

How much is a unit of water and how many litres are in one unit? Here in Bududa district we have just started using water but we highly think we are being cheated in ignorance because even in rain season when we don't use the tap water they charge us over 10,000 shillings, but the water we use can not even make 100 jerricans in a month,please kindly come to our rescue, i , will be glad for your positive response,