I am not familiar with CK30's fuel tanks, but I have a DK45 which developed a leak in the fuel tank after about 5 yrs. My tank is made of the same plastic modern gas cans are made from (I think HDPE), although somewhat thicker. I suppose most fuel tanks are made from plastic, and I can actually see some advantages; apparently price NOT being one of them. I believe it cost over $500 for the part (I can't remember the exact price), and (I was told) it had to come from Korea, it took 2+ weeks to arrive.
A crack developed in one of the bottom corners of the tank; and, in my mind, it was clearly defective material. There was no chafing, rubbing or wear; and there is no way it could have been hit. I have seen very similar cracks develop in plastic gas cans.
There are plenty of You Tube videos on "welding" HDPE; and I seriously considered trying it, but the tank is SUCH a pain to replace, and it seemed kind of an 'iffy' repair. I decided that I didn't want to have to go through that twice.
That happened about 5 yrs ago; now every time I go out to my tractor, I nervously look for the tell tale puddle of diesel under it.