The longevity of the network depends on making the correct route decisions. The term "optimal routing" in wireless sensor networks refers to selecting the best path among the available routes in order to reduce energy consumption and increase network lifetime. Numerous optimization algorithms considering parameters like energy remaining in a node, node distance, network topology, and link quality when choosing the best routes. In order to enable data aggregation and energy-efficient routing through the CH, optimal routing techniques are typically implemented in cluster-based WSNs. In Heterogeneous WSNs (HetWSNs), reliability studies pertain to the network's capacity to deliver information to the base station. Extreme weather conditions, sensor node battery depletion, hardware and software malfunctions, and other factors all have an impact on a heterogeneous WSN's reliability. This article examines the application of optimal routing to both chain-based HetWSNs and also focuses on reliability studies in HetWSNs with chain-based connections that use optimal routing. For five levels of energy-based HetWSNs, an algorithm known as ORB-PEGASIS (Optimal Routing Based Power Efficient Gathering in Sensor Information System) is created. Our suggested ORB-PEGASIS algorithm increases the network lifetime of the HetWSNs by, according to a comparison of the obtained results with various algorithms, including PEGASIS-E by 68.42%, PEGASIS by 112.8%, PEG-ACO by 60.43%, and IEEPB-KMO by 58.47%.