Two softeners with the same tank size can behave very differently because the control decides when the unit regenerates, how much water it uses to do so, and how much you can see of its state. Judge the control first, then the tank and the resin volume the seller quotes.

Ask how regeneration is triggered

Some controls regenerate on a fixed schedule, counting days whether or not much water was used. Others measure the water that passes through and regenerate after a set volume. Some combine both. Ask which method the unit uses, what it is set to from the factory, and who will set it for your home. A schedule-based unit can regenerate too often in a light-use house or too late in a busy one, so the method matters more than the marketing word for it.

Check what you can read and change

Look for a display that shows the time, the days or volume remaining until the next regeneration, and whether a regeneration is running. Ask whether the settings are visible on the unit or kept only in the installer's notes. If the seller cannot show you where each setting lives, you will need them to change it later.

Check what happens after a power loss

Ask whether the control keeps its settings during an outage and whether the clock resets afterward. A control that loses its program can regenerate at an odd hour or stop until someone resets it. Ask what the manufacturer or dealer recommends after an outage and whether that step is written down.

Check the parts and the manual override

Ask whether the seller stocks replacement control parts, how long they take to arrive, and whether the warranty covers the control separately from the tank. Ask what the manual regeneration button does, how much water a manual cycle uses, and whether it can be run without disturbing the salt or the bypass.

Use the same questions on every quote

Put the same list to each seller and compare the answers, not the brochures. A seller who explains the trigger, the settings, and the outage behavior in plain words is giving you something you can check. For how this site weighs the parts of an equipment review, see How Grades Work: Criteria, Weights, and the A to F Scale.