No, it is not normal for the kitchen line and shower drain line to be connected. In a properly designed plumbing system, different wastewater sources should have separate drainage lines to maintain hygiene and prevent cross-contamination.
The kitchen line is responsible for carrying wastewater from the sink, dishwasher, and other kitchen appliances, while the shower drain line carries wastewater from the shower or bathtub. These two sources of wastewater have different characteristics, such as grease and food particles from the kitchen and soap residue from the shower, which require different treatment and disposal methods.
Having a connection between the kitchen line and shower drain line can lead to various issues, such as foul odors, clogs, and contamination. For example, grease and food particles from the kitchen can accumulate in the shower drain line, causing blockages and unpleasant smells.
If your plumber has identified such a connection, it's important to address the issue and have the plumbing system corrected. A professional plumber should be able to separate the kitchen line and shower drain line, ensuring that each has its own independent and properly functioning drainage system. This will help maintain the integrity and efficiency of your plumbing system and prevent any potential problems down the line.