thanks for the reply. I was more-so wondering if anyone has any personal experiences with topping off with too much water. And how much is too much.
Too much is when you taste the wine, and it tastes watered down. It could be 1/4, 1/10, etc- it depends on the recipe, your goals for the wine, the ABV already in the wine, etc.
I generally make a larger batch, so I top off with the same wine (if I want a 5 gallon batch in the final carboy, I make a 5.5 gallon batch of the wine). I put it in different vessels, just for topping off. So, the wine will be in the 5 gallon carboy in secondary, and I'll have a growler with a bung and airlock with the top off wine. And as I rack and top off, the extra vessel might be a small wine bottle.
That can be a pain, but once you have a lot of wine in your cellar, you can top off with a previously made wine that is similar.
Or, in the case of not having extra and not wanting to use water, you can top up with a similar commercial wine. Pinot grigio is a marvelous addition to dandelion wine, as an example. If it's more than a little, I would simply rack to a smaller vessel. I have tons of 1, 3, 5, 6 gallon carboys and lots of magnum wine bottles and growlers.