Thank you all for the nice comments.
Hi Bruce. That is why I was looking for barrels with removable lids- so I could get inside to tighten a nut on the pipe coming in from the bottom.   I changed the design when I found out about the pipe threads on the plugs.  Each of the white barrels has two screw out plugs. One has a 2" x 11 1/2 TPI thread and the other plug has a weird thread- like a half width thread but it has a 3/4 pipe thread in the center. I  left that one in there and just screwed a pipe into it. That is where my faucet is connect on the far right. I screw a hose onto it!

Cheers, Jim ........................ Variety is the spice of life...............Learn something new every day