So I'm about to jump into my first AG batch. I built bulkheads based on Bobby_M's "No Leak" design posted here but I couldn't find silicone o-rings at any near-by hardware stores. Instead I bought similarly sized black rubber o-rings from the faucet hardware section at Lowes. I'm leak-testing as we speak and so far the design lives up the to name but I wanted to know if those black o-rings are safe for food and can tolerate the temperatures the MLT will hold. Any experience with these things?