The pressure at the base of a liquid column is given by the formula P =hdg. Or h=P/(dg).  If, h ,the height of the liquid column is in metres , d =density of the liquid in  Kgs/metre^3 and g= acceleration due to gravity in metres/sec then the      pressure P is measured in Pascals
It is given that the pressure desired at the base of the water tank tower =  60 Psi.By using the conversion formula                1 Psi = 6895 Pascals ,d= density of water =1000Kgs/Metre^3 and g= acceleration due to gravity =9.8 metres/sec^2 ,we
have h =  P/(dg) 60*6895/(1000*9.8)  = 60*6895/9800=  42.21 metres.Hence the water tank should be at a minimum height of 42.21 metres to provide a pressure of 60Psi at the base of the water tower