Are you talking about pumping from the tank? Usually tanks are located such that pumping is not necessary, especially if the tank is being used for fire flow. However, if you're talking about filling the tank, I think you need to know what the fill rate will be, for example, if the storage tank is to be filled in 8 hours, you will need to determine at what rate the pumps will need to run to for this fill time. Also, you'll probably need to look at worst case, ie, max day flow + fire flow and determine if the tank is sized adequately. The tank should be sized for equalization, fire flow and emergency. AWWA has some guidelines you may want to look at, this would be a good starting point. Hope this helps.
