Plumbing on my new tank, leaky bulkheads.

[kendragon]

Because threads are not good seal surface, any kind of gasket on the outside of the tank will not work. You can fill the gap between the tank hole and thread with silicone and sandwich it with the nut.

 

[JK47]

You can also get a needle applicator and Weldon #4 to inject from inside the hole. You will need to remove the bulkhead to access that area. I just did this not but a few days ago. Much less mess down the road this way