Maseno, located in Kisumu County, is a high-potential rural area and has a rapidly growing population. Due to increase in demand, Maseno’s existing water supply system is becoming unreliable. Therefore, it has become necessary to construct an alternative supply main to supplement the existing water supply system and cater for this increased water demand. The main is expected to supply an estimated 1,416 m³ of water per day making sure that the costs remain minimal. This project was thus carried out to design a technically and economically viable rising main between a river intake 6.675 km away from the distribution reservoir while examining the cost implications of different possible alternatives that result from three different interest rates. The design was carried out in three different steps which included selection of different pipe sizes, using three different pumping durations for the selected pipe sizes and finally applying three different interest rates to the different outcomes. A Net Present Cost analysis was then used to identify the most economically viable design. The cost variables put into consideration included; Capital cost as a result of the pipeline construction and pump procurement, Annual operation and maintenance costs as well as power costs and future pump renewal costs. All the above costs were converted to their present value and thereafter compared. The most cost-effective alternative was found to be that which involved the use of 150mm diameter steel pipe with a pumping duration of 24 hours and at interest rate of 12%.