I hesitate to give further advice -- but here goes.
If this is your first racking at the end of the first week then I would expect that fermentation is by no means finished!
This being the case -- there is definitely NO NEED to top up at this stage. Do not do it! Your new container will have a fermentation lock on it and your must/wine will continue to bubble its product of CO2 through it and maintain its blanket in the new container.
It is ONLY when all fermentation has STOPPED and you go into the process of racking off the lees, degassing and stabilising that you need to ensure that the air space ( because it is air then --no or little CO2) is minimal. The level of the new wine should be to within 2 cms of the bung of your fermentation lock.
At that stage you will have to use some method of topping up. I personally would not recommend topping up with distilled water but it is one way of doing it. You can use some similar wine ( which is what I do -- but then I have an ongoing stock level of about 500 bottles of various wines, both actually in bottles and also in bulk).
Lots of winemakers have a selection of different sized containers suitable for wine storage which also helps. Another frequently used method is to lift the level of your new wine by adding sanitised glass marbles until the surface is to the require height although this does give a small problem when you are eventually siphoning out of your carboy to bottle your wine.
I would recommend that you do a couple of things for your own benefit :-
- Buy a good book on winemaking. I would recommend Terry Gareys' "Home Winemaking. It is written for the US market in terms of the US volumetric measures and so on and is full of very good information for beginners and more experienced alike. It is also very readable and being a real book you can put it on your beside table and read a bit each night before you nod off to sleep or sit in a comfortable chair with a bottle of wine to hand and leaf through its pages. Far better than sitting up at a pc and reading from a screen. It is full of tips for winemakers and if you had had it you would not be ducking and diving for information at this stage.
- Visit Jack Kellers web site several times and have a look round. There is just about every conceivable bit of information you could want there. But it can be a bit overpowering there is so much. Which is why I recommended buying the before mentioned book.
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