How long does average 5lb CO2 tank last you?

[Panderson1]

I've got 3, 2-way manifolds running 6 different kegs. So 3 tanks... Mostly each 2way manifold is running to each 10 gallon batch I do (2 kegs per batch). I also starsan purge each keg before I fill them. I feel like I go through Co2 (the tanks) rather quickly. I haven't been keeping track. There are a lot of fittings to deal with and still wonder if I have leaks. It's a tad overwhelming.

 

[day_trippr]

I agree with the ultimately overwhelming thing.

A five pound cylinder used exclusively for carbonation can bring 24 five gallon kegs of beer to 2.5 volumes of CO2. That's easy enough.
But throw in the Star San purge (which I frequently do if I don't do a fermentation purge) and that'll drop significantly - I assume displacing the Star San is going to use one full volume of CO2 (ie: a keg full). And then if you use the same cylinder for dispensing...well I'm not sure where you (or I) would be at that point.

Which is why I have three CO2 systems just to avoid the brain pain of figuring the above out I have one dual-body system for my fermentation fridges mostly for O2-ingress avoidance during cold crashes and the like, but in a pinch I can use it for carbonating kegs in either fridge. Meanwhile I have a second system dedicated to my cold-conditioning/ carbonation fridge, and a third dual-body system for my keezer.

Now, that might actually seem to be a potential nightmare with all those five pound cylinders - and it would be, had I not picked up a 20 pound siphon tank and transfer hose. Et voila! Suddenly everything became nearly trivial - without having to do any math I just keep track of the siphon tank net weight and make sure to empty it before swapping...

Cheers!

 

[Panderson1]

^ thank you

 

[day_trippr]

Well it's a BS answer, of course, as it basically says 'screw the math and just bail me out'
If you want some hard core numbers you might poke our resident gas physics wizard @doug293cz and propose an equation to solve for the total number of kegs that could be Star San purged, then CO2-push filled, then carbonated, then dispensed.

A calculator that could do all that would be an amazing asset...

Cheers!