I brewed 4 days ago. It was a 4 gal batch that I put into a 6.5 gallon bucket with an S shaped airlock. I used a fresh starter that behaved normally. If I press on the top of the bucket, the water level in the airlock moves. But I haven't seen any airlock activity. I'm 99% sure the beer is fermenting as I almost pass out from the CO2 in my chest freezer fermentation chamber when I open it. I plan to open it in a day or so to dry hop and I can check the gravity then. So I'm assuming the bucket is leaking somewhere, but I don't know where. Should I just replace the entire lid? The o ring around the airlock? Something else? Should I not worry about it? I figure it's not a big deal during the first few days of fermentation, but after I open and dry hop, I assume I want a good, airtight seal.