Installation ends when the unit is connected, but the job is not finished until it is running correctly. The startup sequence is where leaks show up, settings get checked, and the first regeneration proves the drain and brine system work. Go through it in order and keep notes as you go.
Check the connections before any water moves
Compare the installed inlet, outlet, and drain connections with the installer's drawing or instructions. Confirm the bypass valve is in the position the installer specified for normal service. If the unit has a separate pre-filter or sediment filter in the line, confirm it is in place and seated correctly. Look for loose fittings, a missing washer, or a connection that appears to rest on a strained line.
Introduce water slowly and watch for leaks
Open the supply slowly, following the manufacturer's sequence. Watch every joint for at least several minutes. A drip at startup is easier to fix now than after the unit has been running unattended for a full day. Check the floor and the area under the unit, not just the connections you can see from the front.
Set the controls from the installer's written settings
Power the unit and enter the settings the installer gave you. Confirm the hardness setting matches your hardness number. If you do not yet have that number, ask the installer which figure they used and why. Read back each setting before you leave the control. A wrong setting can cause the unit to regenerate at the wrong time or use more salt than it should.
Fill the brine tank and load the salt
Follow the manufacturer's instructions for the first brine fill and the first salt load. Do not overfill the tank or let salt sit above the water line in a way the manual warns against. Record the salt level once the tank is filled so you have a starting reference for later checks.
Run the first regeneration and watch the drain
Start a regeneration or let the unit begin its first scheduled cycle, as the instructions describe. Do not interrupt it partway through. Listen for the normal sounds of the valve moving and check that water flows steadily to the drain. Wait for the cycle to finish before you judge the result, because the unit needs to complete its full sequence.
Confirm soft water at the tap
After the cycle, run the cold tap, then the hot tap, for a few minutes each. Test the water with a hardness test kit or the test your installer provided. Compare the reading with your hardness number and the unit's setting. Check whether lather and rinse behave differently than they did before. If the readings and the feel of the water do not match what the installer promised, contact them before you assume the unit is working.
Keep the startup record with your papers
Write down the settings, the salt load, the test readings, and the name and phone number of the installer. Keep that sheet with your warranty papers and the quote. If a problem shows up later, the startup record shows what the unit was set to and how it performed at the start, which makes any service call faster and clearer.