Return is making bubbling sounds

[Gools]

One of my returns is making a bubbling sound that's driving me crazy. I have a 4 way, and it is the furthest one from the 4 way that makes this noise. The other 3 don't make this noise. Any ideas on how to make it stop.
Thanks

[Sebae again]

Do you have valves on each one to try and balance out the flow ?

[Brent F]

put a piece of air line in it. That will give the air a way to escape and stop the gurgle

[Gools]

I don't have valves on them.

Where exactly would I put the air line tubing? I have anti syphon holes above the water line.

[Brent F]

If it is making bubbling sounds it is probably getting air inside.

Solutions are to eliminate the source of the air or give the air a way to escape.

Hard to say what would work without seeing the actual system. An air line can sometimes be inserted to give air a way to escape.

Do you have large bubbles coming out of the return causing the noise? If so, a tee where the majority of water goes straight and the air goes up can eliminate the sound.

[Gools]

Thanks very much. I'll give that a try.