The pressure being stronger from the water than from inside, does it help to have the lip seals on a “push” position (that is lip seals are inserted from the tail versus inserted from inside, and water is “squeezing” the lip seal toward the lip seal “wall” ) or it does not matter at all ?
Also in the case of single lip seals, does the hollow side go on the water side or is that the flat side ?
You are correct. A lip seal should be installed with the high pressure facing the hollow side. That means the seal gets better with higher pressure.
On where the higher pressure is, that is probably from the water side. But there has been a discussuion about heat increasing the internal pressure. The missing knowledge here lead to builds with two seals in opposing directions with grease between the lips.