the purpose of this research is to determine the pipe diameter of the water pumping system by using engineering economic approach to achieve the lowest total cost.
the study was carried out by using the flow equation of fluid in pipe.
subsequently, the data gained from the flow equation was used to calculate the engineering total cost.
the cost in this study was classified into 5 groups : pipe cost, water pump cost, electricity cost, labor cost for installation, and maintenance cost.
all simulations were done based on case studies.
the diameters of Polyvinyl Chloride (PVC) pipe were specified in the range from 0.25 to 0.60 m., and the flow rate was 50 to 500 L/min.
these conditions were applied to the building height of 20 m. to 48 m.
It was found from the above values of the flow rate that the optimum diameter of pipe should be in the range from 0.035 m. to 0.125 m. which exhibited the lowest cost as 29,208.6 baht to 233,308.87 baht.
in addition, the height of building had no effect on the optimum diameter of pipe.
from the case studies, at the flowthe rate of 200 L/min, the optimum diameter of the height of 20 m.to 48 m. should be at 0.065 m. finally, the simulation model showed that the optimum diameter would increased if the flow rate increased.