you can only pressure test things that are sealed, since laterals consist of a bunch of small holes, you can't.
You just switched your zeo over, likely what's happening is that crusehd zeo dust (happens during shipping/handling) is making it's way through the filter and back into the pool - 2 ways that should be able to eliminate that - vac it to waste, or, add DE to the filter, let run for 1/2 hour, vac on filter and backwash.
Nicole - the dirtier you allow your filter to get, the better it performs - I have a felling you backwash a lot and never allow your filter to collect a nice fine layer of dirt on top of the medium which adds to the filtering capabilities....