Many bottlers wash their bottles in the same spring water that goes into the bottles. I assume that the cost exercise has been done that shows it is more cost effective to do this rather than use mains water.
Using spring water can be a problem if the water contains a lot of calcium, magnesium and some iron. The detergents used in bottle washing have to be specially formulated to take account of the high hardness sometimes encountered and higher concentrations of product are often necessary.
A saving on detergent can be made if a water softener is used, although the running costs of resin replacement need to be taken into account.
If your water is very hard, it is essential to ensure that the dosage of detergent is adequate and that compensations are made for drag-out during the course of the day. The bottles will “drag out” detergent product as they move into the rinse section. Some washers do not have the luxury of a drain time before passing into the rinse.
The consequences of under-dosing can be catastrophic in very hard water resulting in rapid scale-up of tanks and heaters. It is essential therefore to monitor detergent concentration regularly which may be done easily with a conductivity meter. A more sophisticated system involves automatic top-up using a conductivity probe linked into the dosing device.
Scaled-up heater element