I kegged my 2 beers 2 weeks ago and I was force carbonating them at around 10 psi for the first week, then dropped them to a serving psi of around 2.7 while I was away for a week. I got back today and saw that my CO2 tank is completely empty. Are my beers ruined? They have been in the kegerator so they have always been cold.
Get some CO2 on it ASAP. Find your leak, spray star San solution on all the fittings. The beer will be drinkable, might have some shorter time before oxidation becomes noticeable. Drink up!
Taste-test!
Pull a couple. Report back.
Why would this ruin a beer? If it were already carbonated, I can’t imagine that oxygen would impact it in a sealed keg/
There is probably some CO2 still in the kegs, but that is just a guess. I don’t want to pull a pint because I don’t want to lose whatever CO2 might still be in there. My beer is probably free of oxidation but I will probably have to remove the lids before i fill them again with CO2. My 2 kegs are from different manufacturers so I think I got the lids switched and they are not fitting well. The kegs are still new. Oh well, live and learn.
No worries. Just don’t mess with the lids or the kegs until you have the CO2 leak figured out. THen you can swap the lids (if need be) and purge the headspace with additional CO2 to seat the lids again. As stated above, I bet your beer is still mostly carbonated (at least a little bit anyway) and probably will not suffer from any oxidation, especially if it was kept cold.
With the lids sometimes you have to try positioning them 180* to see how they fit. On most of my kegs the lid snaps left of the “In” post for the best seal.
My thoughts. Use the extant carbonation to push the beer (if desired). Leave the gas QD disconnected. Then with a full tank reconnect.
Beer will be fine.
2.7 is way too low for a lid to hold. I have two kegs that can do it, but they are outliers. What type of beers are these? Are you confusing volumes of co2 with pressure?
Your lid should be sealed completely with out any pressure, or you need to replace the seals.
But to answer op’s question. I doubt the beer is ruined but I’d purge the head space again ASAP.
My used kegs always get the lids with the handle positioned to the left of the gas-in post. I always take the left hand path. Just for consistency’s sake 
Thank you all for your input. I swapped for a new CO2 canister today and sprayed the keg lids looking for leaks. Sure enough, I think I just had them switched so I corrected the problem and marked one of them so I will know in the future. I bled off a LOT of headspace, hoping to avoid O2 contamination. I have them carbing again at around 12 psi so Im guessing they’ll be ready to try again in a few days. Disappointed that I wasn’t able to come back home after a week out of the country and enjoy my beers after carbing for 2 weeks.
I experienced the same in the past when breaking in new kegs.
Best advice I ever received was to initially pressurize without clamping down the lid. Just grab whatever you can hold (pressure release valve if ball lock) and then crank the pressure to let the pressure seat the lid. That will allow it to “find its groove”. Then if you over pressurize to around 25 psi you can spray and check for leaks. If none, clamp it down, then give the dial a few cranks to lower the pressure and finally purge the headspace. Then you’ll be all good with sealing and purging at the same time.
The number one thing a person can do to help seat their corny lids is make sure the ring is wet first. Sanitizer is sufficient.
I used to warm them up in hot water, too. I haven’t done that in ages, but it was very helpful when I did. Makes them softer and more pliant to any of the grooves or edges that used keg might have.
Occasional keg lube works for me as well when they start to feel drier to the touch.
I have a couple kegs that will pinhole leak from the lid if I don’t use keg lube on the o-ring every time, even if I seat with high psi. Always seals like a champ for me. I change o-rings a time or two/year as well.