A softener can look fine from the outside. The salt level is where it should be, the control head shows a normal cycle, and the tank is quiet. Then the hardness comes back at the tap, or the water feels hard on skin and dishes, and the brine never seems to reach the resin. In many cases the cause is a salt bridge: a hard crust of salt that forms over an air pocket in the brine tank, leaving salt above the water while the salt below never dissolves.
What a bridge looks like
Lift the lid and look before you touch anything. A bridge shows as salt sitting high in the tank with a gap of air or dry salt between it and the water line. The top may feel solid when you press on it. Mushy salt is the opposite problem: pellets clump into a sludge that does not dissolve normally, and that needs a different fix. Check for both.
Also check the brine level after a regeneration. If the water sits well below the level your manual describes, the brine draw is not filling the way it should, and a bridge is a likely cause.
Break it without damaging the tank
Use a wooden or plastic handle, such as a broom handle with the bristles removed. Do not use a metal bar, which can scratch or crack the tank or damage the brine well. Press gently on the crust and work around the edge until it breaks. Remove the loose pieces by hand. Do not force the handle down through the brine well or the float assembly, since that can bend the float or the parts that control the fill.
Your manual says whether you may add plain water to dissolve a stubborn crust. Follow it. Some models include instructions for this and others do not. If the manual is silent, ask the dealer or manufacturer before adding water.
Check the salt you buy
The salt type affects how often bridges form. Pellet and crystal products made for softeners generally dissolve cleanly. Rock salt often leaves more insoluble material behind, which builds up over time. Keep the bag closed and store it where humidity stays low, because damp salt clumps before it reaches the tank.
Make the check part of every refill
Each time you add salt, lift the lid, look for a crust, and confirm the brine level after the next regeneration. This takes a few minutes and catches a bridge before the softened water fails. Write down what you find, so you can see whether the problem is getting more frequent.
What to ask if bridges keep coming back
Ask these questions before you pay for a service call or a new model. Does the tank have a brine well or grid that the manufacturer says to keep clear, and has it been cleaned on the schedule the manual lists? Is the room humid, and is the lid sealed so moist air does not reach the salt? Is the water fill level set as the manual specifies, or was it changed at install? Could a sticking brine valve or float be stopping the tank from filling? Is the salt level kept below the point where it can bridge against the lid?
When to call for help
If the crust returns quickly after you break it, or if hardness returns with no bridge present, stop trying to fix it yourself. Note the symptoms and when they appear, then call the dealer or service technician. Ask them to show you the brine level and the regeneration step on the control head, so you can check it yourself next time.