What is the sound of water running I sometimes hear in the middle of the night?
When the softener’s ion exchange resin is saturated with calcium and magnesium hardness ions, it must be regenerated. A strong brine solution drawn from the salt keeper tank into the resin tank flushes the calcium and magnesium ions off the resin bed to recharge the resin. Particulate such as dirt or grit trapped in resin bed is also flushed to the drain. This “regeneration” of the softener resin is the flushing sound of water running to the drain that you hear occasionally in the middle of the night.
