I have a couple of kits brewing in FV tubs , fancy doing another kit but dont have free FV tub. But hav an old king keg if I put air lock in top what other issues could I have , ideas!
If your diligent with your Hydrometer readings u won't need an air lock if it means ruining your king keg. Just tighten the lid and then loosen a half turn. After 10 days take a reading each day till it stays the same 3 days running. As long as it's as low as it's expected to be for that kit it is finished. Just make sure u santitose your hydrometer each time u use it and disturb your keg as little as possible.