First all-grain/BIAB, looking for advice

I'm about to start my first all-grain brew day tomorrow, and plan to do BIAB. It's a Lemon-Lime Hefeweizen beer.

I understand the standard mash ratio is somewhere around 1.25-1.50 qt/lb. Is it an issue if I go above this ratio? My BK is 8 gallons, and my only other "large" pot is somewhere around 4 gallons. I plan to mash in the BK, obviously, and had wanted to then dunk-sparge in the 4-gallon pot for better efficiency. But I fear the grain bag will be much too full to do that with more than about a gallon of water. Is it fine to dunk-sparge in a clean bucket? At least that would give me an extra gallon to work with.

Can I do a double-dunk-sparge? (i.e. dunk-sparge twice, in the same or separate buckets) That would help me make up the extra water volume.

Does it even matter if I sparge or double-sparge? Can I just top up with water and go? Or will my pre-boil OG be way off doing that?

Any other ideas on sparging? Running water through the grain, rather than dunking?

This is really the part that's throwing me for a loop. The lack of room in the pot will make this a little challenging the first time around. So, I'm looking for the best way to get up to full volume with the least amount of effort (and NOT buying a larger pot).

Thanks, everyone! I'm looking forward to hearing any suggestions you might have.

I BIAB with an 8 gallon pot as well. You will have a very tough time trying to sparge in a bucket. The grain will expand quite a bit after it soaks up the water during the mash. What I do is this: Mash, squeeze/drain the bag, drain wort from my kettle into a bucket, fill the kettle with my sparge water and heat, put the grain bag back in for 10-15 minutes and stir a few times, squeeze/drain the bag. Then I combine my wort back into the kettle and boil.

That's not a bad idea! I think what I'll do is preheat some water in my other pot to toss into the main brew kettle, just to get it started more quickly. Thanks!

Edit: Is there any reason to NOT increase the water/grain ratio? I could go over 2:1, in my pot, if I wanted. Not sure if that's good or not, though.

After some more reading, I'm seeing a lot of 1.25-1.50 qt/lb ratios. I'm thinking that if I do a ratio of 1.5, I'll use approximately 4.5 gallons for the 12lbs of grain I have. With almost 2 gallons of absorption (around .16-.17 gallons/lb), I'll need another 3.5 gallons for dunk-sparging to get to pre-boil volume. I figure post-boil volume should be around 5.5 gallons. Once I pitch the yeast and add the limeade, that'll push my total volume up to nearly 6 gallons, per the recipe. Does that sound about right? Is my absorption rate too high for typical BIAB applications?

Edit: Looks like BIAB tends to have less absorption, due to draining/squeezing the bag. More like around 0.1-ish gal/lb? That would leave me with 1.2 gallons less water, instead of 2 gallons. So, it would be more like this:

4.5 gallons of mash water
After grain absorption, 3.3 gallons are left.
Dunk-sparge volume: 3 gallons, for a total of 6.3 gallons pre-boil volume (might even go less, depending on how much volume I squeeze out of the bag)

Sound okay?

I've done a bunch of BIAB.....actually all I do. I use http://beerreviewdude.com/biab-calculator/ calculator to figure out my starting water volume. It works pretty good, sometimes I add a half gallon or so for good measure. I boil in a 15 Gal post and my boil off is a little higher. I never sparge. Just put my grain bag in an empty 8 gal pot anf smash the hell out of it a bunch of times with a smaller pot lid and keep pouring the wort back into the boil kettle. Always given me really good results.

Thanks, WhiteEagle! I was planning to smash the bag to see how much water I can get out of it. We'll see! I think what I'll do is put graduations on the bucket, so when I pour the mash out to the bucket, that I know how much I'm getting, especially after I squish the bag. Then I'll be able to measure my absorption rate, too.

Link should work now......

Thanks for fixing the link. I've run into that spreadsheet before. It's handy.

Hey Spiffy, What I would do would be to max out your 8 gallon kettle w/ say 6 gallons of strike water, you can check here to make sure it will all fit here....

http://rackers.org/calcs.shtml/

Assuming 10 lbs of grain and 6 galllons/24 qts strike water....2.4 qt/lb mash ratio, total volume is 6.8 gallons, so good here. Having a larger volume during the mash will hold temps better during the mash rest.

After mashing, this should yield about 5 gallons of wort that can be put on the heat to boil.

Then simply dunk sparge in another 1 1/2 gallons of water in the 4 gallon pot and combine in the 8 gallon for 6 1/2 total preboil. If easier, even a cold water dunk sparge will work, keep it simple. Good luck w/ the brew...

Thanks, wilserbrewer. I thought about using more strike water. But I didn't ask soon enough about it, so I just used a standard 1.5 qt/lb ratio. Amazingly, squeezing the bag reduced my absorption down to under 0.06 gal/lb, so I had more sparge water than I needed.

Are there any issues with having too large of a grist ratio? I'm guessing not really, but I have read somewhere that the enzymes for conversion have less contact with the grain, so conversion can take longer in a thinner mash.