Not sure what the plumber did, but this morning our hot water is full of salt.
I suspect he corrected the unintended bypass loop and then incorrectly reduced the Brine Draw setting and initiated a manual regeneration.
Not certain for your Erie brand control valve, but the Brine Draw and Slow Rinse cycles are typically combined into a single 'Brine Draw' or 'Brine' setting. The 'Brine Draw' setting will be most commonly 60-minutes, causing all of the brine to be transferred from the brine tank to the resin tank within~15-minutes, so the remaining ~45-minutes will cause slow rinse flow to push the brine through the resin bed and out to drain while at the same time rinsing the resin with fresh water.
When the Slow Rinse time is insufficient, some brine may continue to remain within the resin and will exit the softener into the home's plumbing once the softener has completed the regeneration cycle and the softener supplies water to the home's fixtures.