I have been struggling with getting a good seal on the drain holes in my grow beds, which are one 55 gallon plastic barrel split and opened up clamshell.  I'm trying to set up a bell siphon so I drilled holes in the bottom (was the side so it is curved) of the beds.   1st attempt we used bulkhead fittings which cracked due to over tightening, but they were not sealing properly, I'm guessing due t…