Most softener trouble starts quietly. Salt sits a little lower than usual, a puddle shows up near the floor drain, or the taps feel harder than they did a few weeks ago. A monthly walk-around takes about ten minutes and catches these changes while they are still cheap to fix. You do not need tools, and you do not need to open the cabinet or touch the internal valve. You are only looking, listening, and writing down what you see.
Check the salt level against the fill line
Look into the brine tank through the lid or the side window, depending on your model. Note how far down the salt sits compared with the fill line marked on the tank or in the owner's manual. If it has dropped noticeably since last month, that is useful information, since a fast drop usually means the softener is using more salt than it should, or the tank is being topped up on a schedule that does not match your household. Do not pile salt above the fill line that the manual or the tank itself shows. Overfilling makes the next refill harder to judge.
Also look at the surface of the salt. A hard crust, a crater where the water sits, or salt that looks wet and packed together all tell you something about the brine tank. Write down what you see in plain words, such as 'crust on top, water level low.' Those words are more useful to a technician than a guess.
Look at the control display
Stand in front of the control head and read the display without pressing anything. Check that the clock shows the correct time, since a clock that has reset can mean the softener lost power and may regenerate at an odd hour. If there is an error code, copy it down exactly as shown, including any letters or numbers. Many control heads show a short code, and the manual lists what each one means. Keep the manual somewhere you can reach it, not in a box in the garage.
Check the bypass valve position
Most softeners have a bypass valve on the plumbing near the unit. Look at it and confirm that it is in the position the manual calls service, which means water goes through the softener to the house. If the handle or lever is in the bypass position, your household is getting untreated water and you may not notice right away. Write down the position you found it in each month. A valve that someone moved during a plumbing repair, a visiting contractor, or a power outage is one of the most common reasons people think the softener has failed.
Look at the floor, the drain, and the connections
Check the floor under and around the unit for water, dampness, or a faint mineral ring where water has dried. Look at the fittings where the pipes connect, and check the drain line for any water that is pooling, leaking, or running where it should not. A small drip at a fitting rarely fixes itself. A drain line that sits in water or has a loose clamp can also cause odd noise or backflow, so note its position if it has moved.
Listen and note anything new
Stand near the unit for a moment and listen. A softener cycles on and off, and some noise during a regeneration is normal. Write down any sound that is new to you, such as a rattle, a hiss that continues, or a clicking that happens at a regular interval. Describe when it happens, whether during the cycle or at other times, and how long it lasts. The notes do not need to be technical. They need to be specific enough that someone can ask the same question next time.
Turn the walk-around into a short log
Keep the observations on one sheet or in one note on your phone, with the date of each walk-around written at the top. Four lines per month are enough: salt level, display reading, valve position, and anything you heard or saw on the floor. After a few months you will know what normal looks like in your house, which makes changes easy to spot. A technician who can see that the salt dropped faster this quarter, or that the valve has been found in the wrong position twice, can usually narrow the problem down in one visit.
When to call and what to ask
If anything on the walk-around is unexpected, call the company that services the unit and read them your notes in order. Ask them whether the change points to a salt issue, a control issue, or a plumbing issue, and ask what they would check first. Ask them to show you the same items during the next visit, so you learn to read them yourself. If the walk-around turns up water on the floor, a control display that will not hold the correct time, or a bypass valve that you cannot return to service position, stop there and call for help rather than working through the problem alone.