Why does one salt block get used up faster than the other?
This is perfectly normal and a harmless issue. One block goes down faster as this shows where the brine valve is located in the water softener.
The salt is always drawn from the block that is closest to the brine valve, hence it going down quicker.
It is OK for one side to be completely dissolved away before adding more blocks. As long as there is some salt in one of the chambers, then the water softener will make brine and function correctly.
More from Maintenance
For every 100 mg/l of calcium carbonate hardness removed from the water, 46 mg/l of sodium is added.
Non-harmful bacteria grow in water softeners.
Bacteria can be found everywhere and particularly in substances where there are minerals, such as water.