[JayJay]

Mac - I had the same issue but around the outlet fitting, not the column support. I fixed as nkaminar suggests - drain the tank to stop the leak, thoroughly clean and dry (brake cleaner works well), scuff up, then apply JBWeld to the joint (I assume you can get JBWeld in New Zealand? It’s a steel-reinforced epoxy, great stuff). Access will be painful, likely easier and a more aesthetically pleasing job if you remove the tank.