Beer seems to be getting less carbed

[kgetch]

Hi guys,

New to kegging but I have 2 brews in the kegs now for a couple weeks. The Hefe seems to be getting less carbed as I drink it.

These first 2 batches, I added priming sugar to and kegged because I did not have a co2 bottle of lines yet.

They sat in the kegs for about a week. Long story short, got co2 stuff and put the gas to them.

I had them at about 20 psi for 2 or 3 days, then down to 10 psi for about 5 days.

Tried serving at 10 but got mostly foam. Read a little and found that 8 psi seems to be the best serving pressure for my set up and it has been.

BVIP pours beautifully and seems right on. The hefe was more carbed and seems to be going flat. Any suggestions or is this kinda normal as the headspace increases?

[loopie_beer]

The carbonation level is based off volumes of CO2. So, most hefe’s are carbed at 3 volumes. As you drink the beer the headspace gets bigger. The beer off gasses to fill this headspace thus losing carbonation. Now to combat that what you would do is set your regulator to maintain the same volume of CO2 absorbed into the beer. So, when you lowered yours to 8 psi the beer is off gassing losing carbonation to fill the headspace and the regulator is only pushing 8psi. To clear things up I will give you an example:

Say your beer is at 34* and you want 2.5 volumes of CO2 for carbonation (average for most light lagers). You need to set the regulator to 9 psi to carb the beer.

If you carb your beer at 9 psi over time and leave it there to serve the carbonation won’t change. If you drop the regulator to 5 psi due to foaming issues the beer loses carbonation and will be only at 2 volumes of CO2.

Have you ever opened a 2 liter of pop, drank half of it, and wondered why it was flat a week later? The reason why is because the CO2 off gasses and fills that headspace.

[chuck]

If you take that 2 liter bottle and squeeze the empty space out then put the cap on it will stay fresher longer.