At what point in a plumbing system might electrolysis commonly occur?

Electrolysis in a plumbing system typically occurs at the connections of dissimilar metals. This phenomenon arises because different metals can create a galvanic cell when they come into contact with each other in the presence of an electrolyte, such as water. When two dissimilar metals are connected, an electrical current can flow between them, leading to the corrosion of the more anodic metal. This process can result in deterioration of pipes and fittings over time, which can potentially lead to leaks or failures in the plumbing system.

The other scenarios presented do not directly relate to the specific conditions under which electrolysis is likely to occur. While old pipes can exhibit various forms of deterioration, including corrosion, it is the specific connection of different types of metals that drives the electrolysis process. High water temperatures and low pressure may affect the performance of a plumbing system but do not inherently lead to electrolysis in the way that dissimilar metal connections do.