I just got a 70qt Coleman Xtreme cooler(marine version) and I'm getting ready to make my mash tun. When I removed the drain assembly I realized the hole is about an inch in diameter. A 1/2" nipple is real sloppy in there. Do you think an oring will seal my weldless bulkead or will I need to get one of those flat silicone washers. Anyone else have this issue? I was expecting to have to drill that hole out so a nipple would fit, then it would be nice and tight. Just wondering what others suggest. Thanks