Can't stop air bubbles in one delivery line

[BeeGuy]

In the week since the pool was opened, air bubbles come out of one of the two water delivery lines to our in ground pool. When the pool timer starts the flow, the water coming out of the one line is bubble free but soon builds to a stream of bubbles with a "burp" of air every second. I've replaced the gasket on the Hayward SP 2600 filter basket as well as the impeller seals and gaskets, but that did not help.
My pool store had me stop the pump and depress the handle of the distribution valve until the sand filter was full. Upon restart the bubbles returned to that one line after a minute of two.
Can any of you offer any insight as to why the bubbles come out of only one line and what I need to look for to stop this condition?

[Denniswiseman]

Definately a suction side air leak
Air or gas will seek the highest level
You say you have a salt system, first of all turn off your SWCG and see if it makes any difference
Silicon grease the pump basket "O" ring