It's kind of a cheesy plastic bowl, and the leak is there where the bowl screws to the valve body, I'd really like to get a brass one with the reserve, there is a high flow one in the parts catalogue but with no reserve. With out removing it I can't tell if it's a pipe thread or straight into the tank, you say it has an O-ring or gasket so that leaves me to believe its a straight metric thread, I don't think the NAPA guys will have a replacement.