How do I collect a sample? Throughout fermentation, the sample valve can be used to collect samples and test the gravity. To do this, simply open the ball valve on the GF30 or SF70 and collect the beer in an appropriate vessel. Image: SF70 Related articles How often should I dump dead yeast and dry hops? What is the difference between OG, FG and SG? How do I dry hop in the GF30 Conical Fermenter? Video - Quick Overview of the GF30 Dual Valve Tap Can I use a Mashing/Grain Bag with my Grainfather?