Harvey HV3 - rising water in brine tank issue

[Bobbyboo]

Just reinstalled my Harvey HV3 non-electric twin softener in my house and seem to have an issue where the water in the brine tank keeps rising. The unit is barely 4 years old. The fault developed after it sat empty in a box for 4 months while my house was being built.

 

The water first rises quickly to the height of the salt, and then slowly keeps rising further as I run the water. After about 2 days of normal usage, it actually rises all the way to the overflow. This is before the automatic regen kicks in, but a manually triggered regen causes the water to drop again, about to the level of where the salt sits.

 

I have taken out the brine valve, and all seems ok (riser sits fine within the well, and nothing is jammed). Any suggestions where else to look?

Edited November 26, 2021 by Bobbyboo