I've been force carbonating with the corny carbonation lids http://www.midwestsupplies.com/carbonating-lid-5-gallon-ball-lock-keg-0-5-micron-stone.html
I carbonate each keg for around 6-7 hours (or over night) at 36* F around 15 PSI. I've gotten good carbonation and decent head for the 1st half of the keg. But the last 1/2 or so of the keg is pretty consistently under carbonated with no head whatsoever. I go through kegs pretty quickly, sometimes within 2 days (beer is served at a brew pub) and I still run into the same problem. Any thoughts on why this might be happening? Or any trouble shooting ideas? Thanks a lot!