My return was moving lots of sand in a corner so I bought a new tip for my locline. I just put it on and restarted my pump. Now my main siphon won't pull but my durso style does. It's also making the gurgling noise. I put the durso to finish in my return section and the other two are in the skimmer section. 3 questions: Do I have air in a line? Is the return pump creating a stronger siphon and making that drain work harder? If none of the above then my third question is Do you know what to do? Haha. No valves were touched. I only switched nozzles and restarted. The main drain isn't showing any flow at all.