Adding water to secondary?

Can I add (sterile) water to my secondary to increase the total volume to 5 gallons? Or should I just leave it? I'm about .5 gal off. And if I leave it, do I have to change the carbinating sugar volume? That way I don't create too high of a carbonation.

 

Since your only .5 gallons off I would just leave it and try to find where you lost the extra wort, either too much boiloff, didn't account for trub lose, etc.

 

I agree. Just leave it at a half gallon less. Adding water would dilute everything about the beer.
In the carbonation calculator enter 4.5 gallons for the amount of priming sugar to use. You will find the difference between 4.5 and 5 gallons is miniscule.

 

I would say that it depends on how full-flavored/full-bodied you want your beer to be. I have used extra water in my priming sugar solution before because my final gravity was just a tad high. I adjusted for the extra water when determining my priming sugar amount.

 

It all depends. If you're making Bud Light you should add an extra 10 gallons of water.