A new softener install is a short job on paper and a sequence of checks in practice. Knowing the order lets you spot a skipped step while the crew is still in the house, which is far easier than finding it after the first cycle runs. The steps below are the usual sequence; the manufacturer's manual and your local plumbing rules govern the exact details.
Before the crew arrives
Confirm the location you agreed on is still clear, that the floor drain or the drain line has a route to it, and that a working outlet is within reach of the control head. Make sure the space leaves room to open the tank for salt and for future service. If you measured the space earlier, check the measurements again against the unit that is actually being delivered, since a size that fit a plan can change once the box is on the floor.
Cut-in and connections
The installer shuts off the water at the main, relieves the pressure, and cuts the line to connect the softener's inlet and outlet. Watch that the bypass arrangement is set so water can be turned off to the softener without shutting the whole house, and ask the installer to show you where the bypass handle is and how it works. Check every joint as it is made. Ask whether each fitting is tightened to the manufacturer's specification and whether any push-fit or compression connections were checked by hand after they were made.
Drain line and brine line
The drain line should run with a clear fall and an air gap to the drain, and it should not be submerged in the drain. Confirm the brine line is connected to the right port and is secured so it cannot slip out during a cycle. Ask the installer to show you the end of the drain line so you can see where the discharge goes.
Power on, programming, and salt
Once power is on, the installer should set the control to the water hardness reading from the test, the time of day, and any other settings the manual calls for. Ask to see the settings written down before the installer leaves. Salt should be added to the brine tank as the manual directs, and the installer should show you the salt level mark and tell you the type of salt that is appropriate for the unit.
The first flush and the first regeneration
Follow the flush step the manual gives, which clears the resin of loose material and air before the water is used normally. Ask whether the installer will start a regeneration cycle so you can see it run, and whether they will wait through the first full cycle. During the first regeneration, watch the drain line, the connections, and the floor under the unit. Any drip at a joint should be fixed before the crew leaves, not after.
Walk-through and sign-off
Before anything is signed, have the installer walk you through the controls, the bypass, the salt level, and what the display means. Ask for the install record, the warranty terms, and the manual, and make sure the model and serial number on the paperwork match the unit in the room. A clean install ends with you knowing where the shutoffs are, how the drain line runs, and what the control shows, so the first questions you have later are answered by the paper rather than by a phone call. For the broader buying sequence that leads up to install day, the buyer's guide is the place to see how the steps fit together.