The water control solenoid is “backwards” and/or the adapters that fit either side of it are wrong. If you look at the arrow on the bottom of the valve it shows the direction of water flow. Following that direction, then one side of the valve has ‘pipe’ thread and the other has ‘hose’ thread. There is a barb to attach to one side and a female/female (pipe to hose) adapter for the other side.
The threads are the wrong pairing. Following the threads and the arrow on the solenoid would have the barb on the ‘input side’ of the solenoid and the hose adapter on the ‘output side’.
We will need to get these parts replaced with a proper pairing.
Both sides of the solenoid valve have 3/4" NPT pipe threads. The barbed adapter converts from the pipe threads of the outlet of the solenoid valve to the barb for the tubing, and the garden hose adapter converts from the pipe threads of the inlet of the solenoid valve to garden hose threads to attach to a garden hose.
Just a note, the barbed adapter uses NPSM threads which are compatible with NPT threads but look slightly different.
So you should just be able to thread on the adapters to the opposite sides of what you have pictured. If you can’t initially, there may be some slight thread damage on the solenoid valve. Take your time, be gentle, and be careful to line it up precisely and the garden hose adapter should thread onto the inlet of the solenoid valve.
What fooled me is that the ‘barb’ connector is extremely ‘loose’ fitting on the other side of the solenoid such that when you try to give it a good ¼ turn past snug, it slips. That will never hold a water flow. On the other side of the solenoid, the barb fits nice and tight. Of course the brass connector fits either side ok. I think the issue is with the barb adapter. I’ll buy another one locally that fits correctly.
WARNING: Don’t buy this part. The BOM part documentation is wrong. You need a ¾ FNPT to ¼ Hose Barb – not a ½ FNPT as the documentation states so I ordered the wrong part.
I couldn’t find a good one of those NPT to barb connectors in town so I ordered this one off of e-bay:
I’m hoping this will give me the ability to tighten up the connection enough to keep it from leaking.
Sorry for the wrong documentation on that page @bgmoon. I have just corrected it to link to the component in the Bill of Materials page which has the correct specs and link to the exact one we included in the kits.
Step 4 is still incorrectly worded for both of the adapters (each say they are ½ NPT adapters.)
Ah yes, I just updated the table the first time. Thanks for the eagle eyes! It should hopefully be accurate now