Most softeners run without much attention, which is why a long trip can leave the unit in a state nobody has checked. The steps below are short. Work through them before you lock the door, and give one person the information they would need if something went wrong while you were gone.
Before you leave
Check the salt level. Read the level in the brine tank and top it up to the mark your manual gives for a full tank. Do not overfill it. For a trip of several weeks, a fuller tank gives you more margin, but the mark in the manual is the limit.
Find out how the unit decides when to regenerate. A time-clock unit runs its cycle on a set schedule whether or not anyone is home. A meter-initiated unit regenerates based on how much water passes through it, so an empty house may mean few or no cycles. Neither type is wrong, but you should know which one you have, because it changes what the unit does while you are away. If you are not sure, the manual or the provider can tell you from the model.
Ask the provider whether to leave the water on. Most owners leave the softener in service. Some providers suggest a different approach for long absences, such as a particular bypass setting or shutting the main supply. Ask before you change anything. If you do shut off the main supply, write down what you changed and where the shutoff is, so the person checking on the house can reverse it.
Decide what happens to the water heater. The softener and the water heater are separate decisions. Whatever you choose for the heater should be written down with the softener notes.
Name one contact for the house. Give a neighbor, a family member, or a property manager three things: the provider's service number, the location of the softener and its shutoff valve, and a note on who has authority to call for service. If you rent, confirm with the landlord who owns the softener and who pays for a service call while you are away. The answer to that question often decides who acts first.
Look for a leak sensor. A water sensor on the floor beside the softener and the water heater can alert a neighbor or a monitoring service before a slow drip becomes a flooded room. Place it low and test it once before you leave.
When you return
Run the taps before you use the water. Open a cold tap and let it run for a short time. Some air or slightly cloudy water after a long stop is normal, and it should clear. If it does not clear, or if the water tastes or smells wrong, call the provider rather than waiting.
Check the basics. Confirm the display shows the correct time if the power was interrupted. Read the salt level again. Look at the floor and the drain line for drips, and check the connections on the valve for moisture.
Compare what you found with what you left. If the salt is lower than expected, or the unit shows an error, note it and call the provider with the details. A short written note of the readings and the date will help the next visit go faster. For a longer routine, see the Missouri Water Softener Buyer's Guide, which covers the chapters on care and service.
The point of the checklist
A softener that is ready for a trip is one that someone else can manage if they have to. The salt, the settings, the leak watch, and the contact are the parts that usually fail when nobody is home. Setting them up before you go takes less time than fixing a problem after you return.