3,
At first glance it does not make a lot of sense, so tell us more...
How many returns does your pool have?
Are they all doing this or just this one?
Does the return have a lot of air coming out when you see it?
What happens when you don't point the return down? Why is it even pointing down??
What kind of pump do you have? Single speed or VS?
On the surface I can't see how a return could make a sucking sound??? Is your return just an open port or is it one of those rotating returns?
Thanks,
Jim R.