Deaerating make up water with co2?

[Tegra]

I am moving to pressure fermenting in corny kegs, which requires a few litres of head space. I am planning to go a bit higher on my gravity with the idea of adding a few litres of makeup water when I move the beer to the serving keg.

I understand from Palmers "Water" book, that brewers go to great expense to deaerate this make up water to prevent evil oxygen from destroying the beer (although on a recent Beersmith podcast, Charlie Bamforth seemed to suggest that keeping the beer cool was much more important than oxygen paranoia.)

Some suggest that simple boiling will "remove" the oxygen, but others seem to prove that all this does is reduce the amount and is not worth the effort.

What about the idea of, about a week before the transfer, filling the serving keg entirely with water and then using co2 to push out most of the water, leaving behind only the amount needed for makeup (about 10% of the total volume). Then the co2 is turned up to proper pressure and we wait for the 2.5 volumes of co2 to be dissolved. The finished beer (mostly naturally carbonated by the pressure process) is then transferred onto this carbonated water.

So the big question is "what amount of oxygen will still be left in the water after it has 2.5 volumes of co2 in it"?

Tom

 

[GCGBrewing]

I wouldn't personally make a beer "concentrate," then purposely water it down. I would like just make a 4 gallon batch instead of 5.

That being said, with filling the keg full of water, where would all that water come from? Would it just be unboiled tap water? If so, I think it better to just boil 1 gallon (to purge oxygen and sanitize) and add it to the keg. I would also add it to the keg first (after purging with CO2), so when you transfer the beer it will be well mixed with the water.

I also wouldn't be surprised if it required some aging to let the flavors blend and shed the 'watered down' taste. Had an issue like that with some wine I made some time back.