Hey all just curious about bag size . I just gave a friend of mine a keg to convert to a kettle so he can BIAB. What size bag would he need . Doing 5 gallon batches .
The bag should be just wide enough to fit the kettle inside it, and tall enough that you have at least 3" - 4" above the rim (when the kettle is fully in the bag.) A smaller bag will constrain the grain during the mash, which you don't want to happen.
Second the recommendation to just get a bag from Wilser. He makes a specially shaped bag that works better for converted kegs where the top opening is smaller diameter than the keg itself.