CO2 utilization when force carbing?

[LordHedgie]

I've switched to force carbing beer (set pressure according to chart, roll keg for several minutes, enjoy). Since doing this, I've noticed my 5lb CO2 tank empties about 2-3 times as fast as it did without force carbing. I haven't been able to find a leak, so I'm thinking one of these three things is true:

(1) Force carbing takes a LOT of CO2 compared to dispensing the same corny keg,
(2) I've got a REALLY small leak I can't find with a spray bottle of soapy water, or
(3) I've got a bad connection that only leaks during the rolling process.

What do ya'll think?

 

[ifishsum]

It's #1. I prime my kegs for this reason, and also because it forces me to let them age for 3 weeks before chilling and serving them.

 

[JKoravos]

The beer probably has about 1 volume of CO2 when it's kegged. Typical carbonation is 2.5 volumes, so you're adding 1.5 volumes (7.5 gallons) of CO2 to the beer. I don't feel like doing the temp conversion now, but dispensing uses 5 gallons of CO2 pressurized to whatever level you're using. It probably amounts to about 1.5 volumes of CO2. So, force carbonating uses roughly twice as much CO2.

 

[david_42]

Double is about right. That's one of the reasons I have two cornies for soda water and hook them up to the water line rather than releasing the pressure and filling. The residual CO2 gets absorbed as the cornie fills. I go through a keg of water every ten days or so and at 35 psi, that's a grunch of CO2.

 

[LordHedgie]

Double is about right. That's one of the reasons I have two cornies for soda water and hook them up to the water line rather than releasing the pressure and filling. The residual CO2 gets absorbed as the cornie fills. I go through a keg of water every ten days or so and at 35 psi, that's a grunch of CO2.

You lost me here -- what are you doing?

 

[david_42]

Simple than it might sound. I have a line with a hose connector, a check valve and a liquid connector. When the soda keg blows, I connect it to this line. Because the house water pressure is higher than the keg pressure, water is forced into the keg. The CO2 in the keg gets absorbed.

When I put the fresh keg on line, it chills and absorbs more CO2.

So, rather than starting with flat water, I get two+ volumes of CO2 for free. It also cuts the time to full carbonization from a week to two days.