Many 19L bottles are returned from the customer in a poor state of cleanliness. They may have been stored incorrectly before collection or been abused when used for other purposes.
The delivery and collection operator should refuse collection of abused bottles and the customer should be charged accordingly with the cost of replacement. However, this rarely happens and the soiled bottles are collected and returned for washing.
Bottles which are heavily soiled or show considerable algal growth should be rejected in the checking process before washing. However, many bottles are "borderline" and this is where the bottle checkers need to make a decision to reject or go forward with washing. Mistakes can be made and some bottles may enter the bottle washer and cause costly contamination.
It is preferable to have a pre-washing facility available for these bottles. Semi-automatic equipment is available which makes this task much easier. It is better to use equipment like this rather than depend on "home-made" rigs.
Cleaning by jets and brushes with a hot detergent solution will provide clean bottles, both inside and out. To be extra safe, sanitising products may be used which give both cleaning and disinfection. The bottle then may be added safely to the stock entering the bottle washer.