A long absence changes what each system is asked to do. Walk the house the way you would on a seasonal visit, then add the steps that matter only when nobody is inside to notice a change. You will need a pen, your service records, and the name of the person who will hold a key.
Set the Thermostat for an Empty House
Pick a heating and cooling setting the house can hold without anyone adjusting it. Write it down. Tell the key holder what the setting is and what it should not be changed to. If your heat comes from a gas furnace or a boiler, read the setting against the guidance for that unit. A heat pump or a central air conditioner may respond differently to a wide setback, so check the manual for your model before you leave it on automatic.
Shut Down What Should Be Off
Close the water supply to any appliance you will not run. Dishwashers, clothes washers, and ice makers each have a supply valve. Close those valves and keep the drains clear. Run the garbage disposal with cold water to clear the chamber. Empty standing water from the dishwasher. Leave the washer lid open so the drum can air out. Unplug small appliances that have no reason to stay live.
Check the Water Path
Look at the hoses behind the washer and under the sinks. Replace any that are cracked or bulging before you go, not after you return. If the house has a main shutoff you can reach, know where it is and show the key holder. For a long absence in a cold season, ask your plumber whether the water should be shut at the main and the lines drained. That decision depends on the home and the climate, so make it with a professional rather than from a checklist.
Leave the Garage Ready
Show the key holder how the manual release on the garage door opener works and where the release cord hangs. Confirm who holds each remote, and take the spares out of the car. Keep the electrical panel labels current so the key holder can find the right breaker if a light or outlet goes dead. Name who calls whom if something trips.
Write the Record Before You Lock Up
Note the date of the last filter change for the furnace or air handler. Note the last service visit for each major system. Keep this note with the thermostat setting and the shutoff locations, so a key holder can act without guessing. If you have a home service agreement, keep its paperwork with the note and read the terms on access and visits during an absence. Do not assume the contract allows what you need. Confirm it.
When you return, walk the same list in reverse. Reopen the valves, reset the setting, and check the hoses. For a broader view of which systems to plan around, see the appliances ranked by typical service life page, and use the fall furnace walk-through when the heating season is ahead.