There is an old story doing the rounds about one of the pioneers of the South African wine industry. The story, that will never be verified, says that the wine that always stood head and shoulders above that of its neighbour’s, was made in the early eighties by picking the grapes extremely ripe and then adding water. The fruit intensity and softness of the wine’s tannins were unknown at the time, and the wine was very popular.
In the USA the humorously named practice of humidification and more officially named, rehydration of grapes is quite legal. The California Wine Institute sought official approval from the authorities for adding enough water, to replace that which was lost from grapes through field dehydration, and it was granted. The exact amount of water that can be added is not stated outright, but it could be very high. Water is also allowed in California to bring the sugar down to a level that will prevent stuck fermentation.
In Australia a maximum legal amount of 70ml of water per liter of wine may be added, but only during the normal course of winemaking, and not necessarily for the dilution of wine or juice. There are rumours that the practice of the addition of water derived from reverse osmosis is also used from time to time, since it is derived from grapes anyway.
All the practices of water addition that I mention here are to improve the wine and not to dilute it. It is there to prevent stuck fermentations and to improve the flavour and tannin structure of the wine while not having ridiculously high sugar levels.
South African law will soon be catching up, and a recent notice from Wine and Spirit Board stated that, “Pending further directions from the administering officer of the Liquor Products Act and the Wine and Spirit Board, water will be able to be added to certified wine for the correction of moisture losses in grapes. We will let you have above-mentioned directions as soon as they become available.”