The answer to 'why is my water softener no hot water' is that a malfunctioning water softener can cause issues with your hot water. The water softener may not be properly softening the water, leading to mineral buildup in the water heater that reduces its efficiency and ability to heat the water effectively.
Some common causes include: the water softener is not regenerating properly, the softener resin beads are exhausted, or there is a mechanical issue with the softener's valves or controls. This can lead to hard water entering the water heater and causing scaling, which insulates the heating elements and reduces hot water output.