You had a softener installed, and now the shower still feels squeaky, the kettle still crusts, or only the kitchen tap runs hard. Before you assume the unit is failing, check whether the water is reaching the softener at all. A softener that is sitting in bypass passes your hard water straight through to the house, and it can look like a dead unit when it is really just not in the flow.
What bypass means in practice
Most softeners sit on the main line with a set of valves, often called a bypass valve, that lets you route water either through the resin tank or around it. In service, water enters the softener, gets treated, and then leaves for the house. In bypass, water skips the tank and goes directly to your taps. The bypass control is usually a handle or a small set of handles on the valve assembly, and the position is easy to change by accident, especially after a service visit, a plumbing repair, or when someone is trying to shut off water to one fixture.
The signs to check first
The most common sign is hard water at every tap, or at most of them, even though the softener is installed and was working when it was set up. Another sign is that the water is soft for a short time after someone has been near the valves, then hard again. Some people notice that the water tastes or feels different at the hot tap versus the cold tap, which can mean the bypass is partly open or the valve handles are not set the same way. If you have a simple hardness test kit or strips, test water from a tap that normally runs hard, then test again after you confirm the valve position. Compare the two readings with the same method so the comparison is fair.
What to check on the valve
Look at the valve assembly on the main line near the tank. Find the handle or handles that control bypass and confirm they are in the service position described in the manual or on the label the installer left on the unit. Do not force a handle that resists. If the valve looks mismatched, with one handle turned and another not, stop and read the labeling before moving anything else. If there is no label and no manual, ask the installer or the company that serviced the unit to show you the correct positions in person.
When to call for help
If the valve is in service position and the water is still hard, the cause may be somewhere else, such as a regeneration that has not run, salt that has run out, or a control that is not responding. Those are separate problems and need a different check. If you are unsure which position is correct, or you see a leak around the valve, shut off water to the unit using the shutoff valves before you touch the handles further, and call the company that installed the softener. Ask them to confirm the bypass position over the phone, and ask them to check it on the next visit if you cannot confirm it yourself.