No, but you should get the wine out of the demijohn, clean it and transfer it back. You can put it in food grade buckets while cleaning, then get it back in the demijohn. You are going to have to rack it a couple of times more. It is much easier to just rack it into a different carboy or demijohn than rack it out and back again. Reason for doing this is you want to get it off the gross lees so they do not impart off flavors into the wine. Arne.