A softener does its job in two steps. Each regeneration draws salt solution from the brine tank to recharge the resin, and the charged resin then pulls hardness out of the water that passes through it. When the salt step stops, the resin stays loaded with hardness, and the water reaching your taps starts behaving like hard water again. The symptoms creep in slowly, so the brine tank is often the last place anyone checks.
What a salt bridge looks like
A salt bridge is a hard crust that forms above the water line, often when humid air or a loose lid lets moisture into the salt pile. Water sits underneath the crust and cannot reach the salt above it, so no brine forms. Look into the brine tank with a light. If the salt level has dropped but the pile still looks full, or you see a dome-shaped shell with an empty gap beneath it, you probably have a bridge.
What mush looks like
Mush is the opposite problem: salt that has dissolved into a sludgy layer at the bottom or turned into a paste. It usually comes from the wrong salt type, too much water in the tank, or a pile that has sat wet for a long time. Mush can clog the brine line and the injector, so it can stop regeneration even when the tank is not empty.
Signs you should not ignore
Keep a short list of these: spots or scale on fixtures that were clean before, soap that lathers poorly again, a salt level that stays flat between refills, or a brine tank that smells or holds standing sludge. Any one of them is a reason to check the tank before the next service visit.
What to ask the technician
Ask whether the brine tank is inspected at every visit and whether any crust or mush is cleared out, not just topped up with more salt. Ask which salt type the manufacturer recommends and whether your current salt matches it. Ask whether the brine well and float are checked so you know the tank fills to the right level. If the control keeps a regeneration log, ask what it shows. Finally, ask what they will do to keep the crust from returning, such as keeping the lid sealed and the water level in range.
Do not break it up without a plan
If you find a bridge, you can loosen it with a wooden or plastic tool, but only after you have handled the water supply and the softener's power as the manufacturer directs. If you are unsure about the power or the bypass setting, leave the work to the technician and report what you saw, with a photo if you can take one.