The helium gas pressurization system utilized in the liquid stages of ISRO’s launch vehicles is critical for ensuring the cavitation-free operation of engine. The system used in the operational stages employs metallic (titanium) spherical containers for helium gas storage. However, with advancements in technology, composite overwrapped pressure vessels (COPVs) have emerged as a superior alternative due to their high strength-to-weight ratio, leading to payload gains. Compared to titanium, COPVs with carbon fiber reinforcement and a titanium liner have lower thermal conductivity. This can significantly affect the gas temperature history during the expulsion process, which governs the requirement of gas storage for the pressurization system. This paper reports the impact of replacing the titanium gas bottle with COPV, on the pressurization system performance, particularly addressing the shift in blowdown point. Utilizing a lumped parameter numerical model and the SINDA/FLUINT network analysis tool, the research assesses and compares expulsion rates and blowdown characteristics between the two vessel types under similar outlet conditions. Both the numerical and network analysis models are validated with flight and test data, revealing potential shifts in the blowdown point due to the adoption of COPVs.