A salt bridge is a hard crust of salt that forms in the brine tank and sits above the water. The salt still looks like it is there, but the water underneath cannot reach it, so the softener has no brine to draw from. The unit can keep running on its schedule while the water coming into your home gets harder again, which is why this is worth checking before it shows up as spotty glasses or a stiff shower.
What to look for
Open the brine tank cover or look through the window if your model has one. Compare the salt level with the water line. A good setup has salt sitting above the water with a little water at the bottom. If you see an empty gap between the salt and the water, or a dome of salt with dry space underneath, you probably have a bridge. Some units have a salt level indicator or a low-salt light. Those show when the level is low, but they do not always catch a bridge, so a quiet light is not proof the salt is fine.
Set a check schedule and write it down. A note on the cover or a repeating phone reminder is enough. The right interval depends on how fast your salt goes down, which you learn over the first few refills. Once you know that rate, check a little before you expect the salt to run low, not after.
Who breaks it up
For many homeowners, clearing a bridge is a short job with a wooden broom handle or a similar blunt tool, done slowly so you do not crack the tank or knock the float out of position. Read your owner's manual first. If it says to shut the unit off before you reach in, do that. If it warns against tools that could damage the float or the brine well, follow it. If the manual does not cover it, ask the company before you start.
If you break a bridge and the water is still hard a few days later, that is a service question, not a reason to pour in more salt. Call the company and tell them what you saw and when.
Divide the work before the first problem
You will usually own the regular jobs: checking the level, refilling with the salt type the manual lists, keeping the bag dry and covered, and clearing a bridge if the manual allows it. The company usually owns the control head, the valves, and anything your service agreement names. Those lines differ by company, so ask rather than assume.
Ask these before you need them:
Does my model have a salt-level sensor, and does it detect bridges or only low salt? Which salt type does the manual list, and do you sell it? Does a maintenance visit include checking for bridges, or does that stay with me? What should I write down or photograph before I call, so the first visit is not wasted? Who pays if the problem turns out to be a bridge I could have cleared myself?
Get the answers in writing or in the owner's packet. When you can name who does each job, a bridge becomes a five-minute check instead of a surprise.