If you have it secured through the side of the tub like a bulk head, you'll probably be okay. I had mine just pulled over the side and held in place by a zip tie. When the flow slowed down, it would run under the bottom of the pipe and drip off at the lowest point, which was not over the tank. A bulkhead fitting should still drip into the tank.

You may be having flow issues from tank to tank. If you fill too slowly in the siphon tank, you'll dribble out, but not be able to create the siphon to start draining. If you fill too quickly, the siphon will have problems breaking the seal to turn it self off. Filling too slow will leave you with a full container that drains as quick as it fills. Filling too fast will leave you with an empty container that drains as fast as it fills. I could have my siphon work consistently for about two weeks at a time. Finally, it would stay full and I would just jiggle the siphon every time I walked by (at least once in the morning, and several times at night) to trigger the siphon. I was still able to grow my jalapeno like that.