I have a water softener I installed. I did a test using the test strips, and it said the grains of hardness was 11... The city says its more like 15-25. What would happen if I set the grains setting on the softener to high? If I set it to 25 and it truely is 11 would there be any adverse effects other than it would use more salt??
You are correct in that if the water only has 12grains and the unit is set for 25grains there will be an increase in the salt usage.
Checking every 3 months to see what the city is delivering in water hardness lets you change the settings for different parts of the year if needed.
Say the first of May the water goes from 11 to 20, then in the middle of April you could change the setting so that you always have treated water and
little waste of salt, then if the water goes back to 11 in the middle of Sept then the 1st of Oct you could move the setting back down.
Learn the changes in the city water to get the best out of your system so that it is not over or under worked.
Personally, I would set the softener to the highest hardness during the year (apparently 25 in your case) and accept using a bit more salt than might be used with continual fiddling. Even with continual fiddling you will almost certainly end up with hard water at some point during the year and then to get the softener working properly again it is necessary to go through a process--two back to back regenerations at max salt dose--to get things back on track.