An aging softener puts you in a two-option decision with a lot of guesswork. A repair keeps the unit you already have working. A replacement starts a new service life. The useful question is not whether the unit is old but whether the next repair costs less than the years it buys you.
Get the repair quote in writing, line by line
Ask the technician to list each part, the labor, any separate service fee, and whether any remaining warranty covers the work. A quote that says only valve repair gives you nothing to compare. Keep the written quote so you can check it against the invoice.
Count the repairs the unit has already needed
Look at your own records or ask the provider for the service history. A tank that has needed the same part more than once is often showing wear in other internal components too. One expensive repair on a unit that has otherwise run cleanly is a different case.
Compare against the full cost of a new unit
Ask for a replacement quote for the same capacity and the same install scope, including removing the old unit, reconnecting the lines, the drain, and any site work. Put the two totals side by side. Then estimate how many years of reliable service the repair adds, and whether you expect a new unit to last longer than that.
Check the water you are still getting
An old unit can keep cycling on schedule while it softens less well than it used to. That costs you in soap, scale, and appliance wear even though the unit looks like it is running. Test the water after the softener before you decide the unit is fine. Note when and where each sample was taken so the readings are useful later.
Decide and keep the paperwork
If the repair is small and the unit is otherwise sound, fix it. If the repair is large and the unit has a pattern of failures, replacement usually makes more sense. Whichever you choose, file the quote, the invoice, and the test readings with the unit's history. For a wider view of reading a cost quote, see the Missouri Water Softener Buyer's Guide.