I was topping off my batch to make it reach the 5 gallon mark and I accidentally added too much water. What will this do to my beer? Is there anything I can do?
How much water, a little bit of water will not hurt. A lot of kits I have done say to fill a quarter gallon over the 5 gal mark, I assume to make up for the lost volume in the trub and such.
Your O.G. will be lower. If you take another reading you'll know what the effect has been. If your kettle is large enough you can reboil down to 5 gal and chill. It won't be perfect, but it should be closer to what you were aiming for