Yes I did have the problem initially, but on the 90 degree fitting for my returns, I drilled a small hole. When the pump shuts off, this small hole breaks the siphon. So no worries thus far. I also did test it with where I plan to have my loc line. It only fills my sump up about half way. The main issue is the noise from the water exiting the drain lines in the sump. I will try to extend them into the water, but I'm worried I will then get a gurgling / bubbling effect. Do I extend it just under the water surface or almost to the bottom of the tank?