Mixing two small batches?

Due to limited equipment I was wondering if it is possible to brew one 2.5 gallon batch (BIAB) and then another directly afterward and mix the two in one fermentor? Would I only have to pitch yeast into the first one? Thanks in advance

Are they both the same beer? If so, then just brew, combine, and then pitch the yeast into the whole thing.

Yes they are, I am just worried about letting the wort sit too long without any yeast? is that a negligible risk?

How long are you talking about letting it sit? I was under the assumption that you were going to brew both in the same day. I am not sure, but I believe 24 hours is the deadline as far as unpitched wort goes. A lot of guys leave it overnight to cool, but the only other practice I am aware of is cooling a wort before the boil by extract manufacturers for a cleaner beer and less contamination problems due to the colder temp. The longer a wort sits, the more likely infection. I'd suggest brewing both in the same day and combining, but no more than 24 hours apart. More experienced brewers will have better advice I'm sure.....

Alright, thanks man! I am brewing them both the same day. It should only be 2 hours or so because I am doing biab for this one. I think I was being a bit overly cautious.

Are you brewing extract or AG?

If extract, you can brew your first 2.5G batch as if it were a 5 gallon batch, like a partial boil, using all other ingredients (specialty grain, hops etc.), except use only 1/3 or 1/2 of the extract. When done, chill and flow into your 6.5 Gal fermentor.

Then prepare the 2nd half of your batch by dissolving remainder of the extract in another 2.5 Gallon of 200°F water, to pasteurize. Chill and add to your first half in the fermentor. Stir, oxygenate, and pitch yeast.