Seal tap shank through collar?

[laxation]

I've been getting a bit of water in my keezer - not sure why yet. Could be a bung seal, or even just because it's an old freezer...

But I don't have silicone around my tap shanks. Does anyone do this? I drilled a 25mm hole, so there's only ~1mm gap, but still potential to let air in I guess.