A Culligan water softener bypass valve is a plumbing component that allows homeowners to temporarily isolate their water softener from the water supply. This can be useful for maintenance or repair purposes, or if the softened water is not desired for certain applications. The bypass valve is typically installed at the inlet or outlet of the water softener, and is operated by turning a handle or lever. When the bypass valve is open, water will flow through the plumbing system without being softened, while when the bypass valve is closed, water will flow through the water softener and be softened.