Intake to water pump hose for air gap intake??

ok, simple question. My first engine build. Newly rebuilt 340 and I put an edelbrock air gap intake on. I noticed it has a female thread on the intake for the hose to the water pump. The small hose that goes between. Anyone know what that thread size is? Is there a special hose/adapter I am supposed to use? One of them things I've been meaning to do..

Thanks for the help...