The time you need to leave the sauerkraut is closely dependent on a couple of factors, temperature, and saltiness. It also depends on how sour and/or crunchy you like it to be. Taste after 7 days to check the flavor and texture. It really depends on how hot it is but it should not take any longer than 3-4 days for the fermentation process to start. During hot summer days, it is a short process- 3-4 days for this to get into the fermenting stage or less if you add hot or lukewarm water. During the winter period will take longer but to speed up the process you may add hot water and a dash of sugar.