Subject: Re: DIY CO2 and leaks Inside the cap of the 2-liter pop bottles I use is a thin flexible bluish gasket, which comes loose when I drill a hole in the cap. This gasket can't be discarded, or the cap will leak. I put sealant on both sides of the gasket and put it back in the cap. Then I put the tube through and slop sealant around it inside and out. This works fine. Cliff Lundberg San Francisco