Safe to add water to primary?

[BrewMasterG]

I brewed a batch of double IPA last night and added it to my primary fermenter at about 1 AM. It's now 12:45 PM the following day. My OG was 1.080 and the target was supposed to be 1.070-1.040. My primary is currently filled to the five gallon mark, but I am noticing now that nearly 3/4 of a gallon is sediment on the bottom of the fermenter. So, my higher OG is likely the result of not actually having a full 5 Gallon batch. My plan is to add 1/2 a gallon of water to the fermenter before an active fermentation begins. I was going to do this in the same way I would transfer beer to a secondary...except this time I am moving water (purified and at room temp) to my primary. I have a second fermenter w/spout, so it wouldn't be a challenge. I could just remove the airlock, feed the tubing into the fermenter (about halfway), open the spout and send in some water. Is this a bad idea? Should I just leave the beer alone and let it do it's thing? Or does it make sense to add more water in an attempt to reach an OG closer to the target range for this recipe? Any comments or suggestions would be very much appreciated. I want to make a decision by tonight before fermentation really takes off.

 

[Yooper]

If you just brewed last night, you could open it up and just pour it in. Oxygen is important at the beginning for a healthy fermentation, and you should pour/splash/aerate your wort anyway.