27 CFR §24.186

1. (a)Accidental additions of water totaling 1 percent or less of the volume of standard wine. When in the production, storage, treatment, or finishing of standard wine, water is accidentally added to a standard wine in an amount that does not exceed 1 percent of the total volume of the wine, such wine shall remain standard wine and the proprietor need not take any action to correct the wine.
2. (b)Correction of accidental additions of water. When in the production, storage, treatment, or finishing of standard wine water is accidentally added to a standard wine in an amount that exceeds 1 percent of the volume of the wine, such wine may be corrected by removal of the accidentally added water from the wine in accordance with § 24.252.