Cross-connected pipelines may be to blame for the cold water you’re experiencing.
In the past, pipelines that were cross-connected were helpful. Back then, house builders had to come up with alternative methods for allowing the flow of hot and cold water into showers, because parts like mixing valves weren’t yet available. They installed cross-connected pipes as a solution.
Those cross-connected pipes were essential in the past, but modern innovations that have made hot water more accessible have made them obsolete. However, those cross-connected lines could still exist, and they could be the source of your current issues.
Cross-connected pipes aren’t necessarily the issue, though it’s difficult to tell. To determine that they are the main reason for your lukewarm showers, you’ll frequently need to use the method of exclusion.