I drill a hole a little smaller than the CO2 tubing. Then I pull the tubing through for a tight and leak-proof seal. I've built over 20 of them over the past year for people locally and not a single one has leaked. (Maybe they're not telling me? :mrgreen To make it even less likely to leak, drill the hole through the top of the reactor, NOT the side. That way, water is pulled AWAY from the connection.IUnknown said:The only thing I hate about DIY, at least the one I made was the nipple attachment for the Co2. I never found a good DIY part and so I ended up using glue and it was always leaking on me.