A softener regenerates on a schedule or by water use. During regeneration it flushes the resin and sends water to the drain. A healthy unit does this for a short, predictable time and then returns to service. A unit that cycles too often, or that stays partway through a cycle, can run a lot of water with no one at the tap. The first sign is often not the softener itself. It is the water meter, or a bill that is higher than the household's habits explain.
Run the meter test
Pick a time when no one will use water for at least an hour. Turn off every tap, the dishwasher, the washing machine, the ice maker, and any irrigation. Note the meter reading, wait, and read it again. Any movement at all with everything off points to a leak somewhere, and the softener is one of the places to check, not the only one.
If the meter is still for an hour, repeat the test at a time when the softener would normally be regenerating, using the schedule on the unit or the time the installer set. Movement at that time suggests the softener is drawing water on its own schedule.
Check the drain line
Look at where the drain hose or pipe leaves the softener, and watch it while no water is being drawn elsewhere in the house. A steady trickle with no regeneration expected is a warning. A unit that is cycling normally should be quiet between cycles. Do not open the valve or take the unit apart to look. Note what you see, with the time, and move on to the control display.
Read the control display
Many softeners show the current time, the days since the last regeneration, or a regeneration history. Write down what is shown. If the display shows a regeneration running longer than the time the installer described, or shows a fault code, record the code exactly as it appears. If the unit keeps no history, a cycle count is still useful if the service provider can read it.
Decide who looks at it
If the meter test shows water moving with everything off, or the drain runs at times when the softener should be idle, call the service provider rather than changing settings yourself. When you call, say what you tested, the times, the meter readings and any display codes. A written description like this gets a technician to the likely cause faster, and it saves you from paying for a visit that is only a repeat of the same question.
Before the call, check the service terms in your paperwork, since some plans cover diagnostic visits and some do not. The buyer's guide covers what to ask a provider when a unit behaves unexpectedly, and our rankings and field guide list the providers we reviewed for response and documentation.