Heat exchangers are the equipment used in variety of industries at all levels related to heat and thermal systems. Using heat exchangers at maximum efficiency are to reduce the amount of energy lost that impacts on environment and manufacturing cost in the industry. This research focused on comparing performances of two heat exchangers; two double-pipe heat exchangers were fabricated domestically with two different welding techniques (flare and Argon welding techniques). Both heat exchangers were tested on the same experimental setup and investigated for their thermal efficiency. Their working fluid was water, hot water and cold water flowed inside the heat exchangers were arranged as parallel (co-current) and counter flow configurations. Thermal efficiency when hot water and cold water flow rates varied in the range from 0.5 to 2 liters per minute, were also investigated. The results showed that the second heat exchanger fabricated with the Argon-welding technique showed the better thermal performance than that of the first heat exchanger fabricated with the flare technique. The thermal performances of the second heat exchanger were varied from 92% to 99% while the performances of another heat exchanger were varied from 32% to 38%. Therefore, the heat exchanger manufacturing played an important role to the heat exchanger performance. The same heat exchanger design but different fabricating technique caused lost in heat transfer process which affected the thermal performance and operating cost of the industry. © Published under licence by IOP Publishing Ltd.