Dispenser Module with odd M20-14 thread

I printed one of the Dispensers for the Garden Tower and took it to Home Depot to find the correct tubing. Well I couldn't find the tubing size needed.
I thought I would need a 1/2"? Is that 1/2" OD? Because it's not 1/2" ID.

I also had a problem with the Pump Adapter. The .51 barbed fitting was too small. So I used Solidworks to make it .52 which worked very well! BUT I couldn't find the correct thread type. Which later I found out to be a mix between M20 and 14 threads per inch or a pitch of 1.83mm ish. So When I was rebuilding this part, I thought, why do I want a tubing attachment to this unit? So I turned it into threads.
However, which threads do I use?????? I decided to keep with the same weird M20-14 for the adapter.
I think it turned out nicely but now there are no other threads that fit it other than my own adapter that you can print. in Remixes.

https://www.thingiverse.com/thing:5929533