that looks like an RV 1/2" compression fitting. it should look like the fitting that's on your water pump. you need the plug like the one in the picture that I gave a link to. take a good pic or two, go to a RV shop and they can fix you up. I have never seen a compression plug at a regular hardware store. highdesertranger
you know both should work. you should be able to find the plug at a regular hardware store. the key here is notice the plug is hallow in the center, the plug must be this way due to it's being used on a compression fitting. highdesertranger
So imagine that... I go back to lowes and find what I needed, because I didn't asked someone that worked there, and went with what I knew would work.. Thanks to all of you!
Lesson.. go with your gut....
It fit like a charm and only cost me 94 cents... Now we can get some water in the tank,