Why Water?

I would not do that, I use wine to top off, not juice or water. I use any red for a red, white for a white. Adding juice may make the end product unstable or may not. If you want a non dry wine juice is a good option. It depends on what style you are making and what steps are taken to deal with the sugar in the juice.

Joe

Well for concentrate kits, you just add the water back to replace what was taken out.

For other wines it is all a matter of balance. You only want so much fruit for a wine of x% alcohol and y% residual sugar. To mush fruit and you have alcoholic juice. To much sugar and you have alcoholic kool aide. To much alcohol and you have rocket fuel.

You do not want to add juice to top off unless you want to make a sweet wine. The juice has sugar, of course, and it does not take much sugar to turn a dry wine sweet. If you want to sweeten the wine you may use juice. But then you must use sorbate to prevent it from refermenting and you must realize that you may cause it to become cloudy again. You might create a new fining problem even after it has cleared.

If you are using kits, they are designed to be topped off with water so they will be balanced. If you are making your own wines from juice or fruit, you can design it to be topped off with water or to be topped off with wine. I rarely top off these wines. I just rack into smaller containers.

Ray

Do not top up kit wines with water. I always use a similar type of wine from my "cellar". I never use water to top up

The issue was not topping up after racking, but bringing the volume of the must from 3 (the concentrate) to 6.