Bderick67;1279585; said:With your xp3s make sure the "primming cap' is on tight on the intake tube. Also make sure the baskets are stacked right inside the cannister(they should fit tight into each other and the top should secure them in place). If the basket are not fitted you'll pull air into the impellar(this air is in the cannister and you can see it by tilting cannister to the side).
I believe Bderick has hit the nail on the head. I had the EXACT problem you are describing in a tank with an XP3. I went over and over the tubing and inlets looking for a leak and was endlessly frustrated

Finally realized that what was happening was what Bderick describes, the pump sucking in air from tiny gaps between the top basket and the pump housing. Personally I solved the problem by restricting the flow on the outlet so that the canister filled COMPLETELY with water so there was no air gap around the outside of the filter baskets.
I hope that made sense...its hard to explain...

