Oversized Brite Tanks - Wasted CO2 / Spoilage?

[TDAWGG]

I am considering several different used brite tanks and am thinking about going 2 times the brewery size. This would allow double batching into one brite tank. However there are many times that I might just brew a single batch and that would leave a lot of empty space in the tank.

I would purge the tank with CO2 but that leaves several questions.

1. Assuming a batch size of 150 gallons and a tank size of 300 gallons how much C02 would be necessary and is this a big waste.

2. Would there be a large chance of spoilage with the larger tanks even after the CO2 purge.

Any other pros/cons I should be weighing out. Economics play a large role in the decision as you can sometime get a bigger tank for a cheaper price.

Thanks for your help!

[Matt Dog]

I'd always go for the bigger tanks. Sure you waste some CO2 but you already plan to double batch into them. If your using them as true brite tanks and filtering into them and packaging quickly you can clean them with acid under pressure and go right back into them with minimal CO2 loss. Lots of breweries have multiple size fermenters and only partially fill brites at certain times. No worries on spoilage unless you are not clean to start with. Most brewpubs serve from brites and by the end you may have .5 -1 Bbl in a 30 Bbl brite.

[BrewinLou]

Double size them. Purge CO2 in the bottom and air out the CIP arm until CO2 comes out. There is no more chance of infection with a single size if you clean, sanitize, and hot rinse than there is in the double.