Thumper down tube

[Robbiejames]

Hello, I have a new still that was purchased from Amazon. I put it together and found that when the vapors leave the pot and enter into the thumper the down pipe(from the lid to the bottom) inside the thumper is not a part of the still. Which defeats the purpose of the thumper so I need to know what materials I can use to make one. The nipple inside the thumper lid is 1/2” outside diameter. I went to a local hardware store and the only thing they had to fit it was PEX, brass and galvanized pipe. Any help would be great. Thank you in advance.