Hello, just bought a new SW 4200 and I'm having a problem using the wash out port on the mulching deck. I attach the hose, engage the blades and very little water comes out. I need to sit my daughter in the seat to keep the blades going while I push the house into the adapter to get a decent flow. Even then, the deck doesn't clean, only a few blades, not the clumps. Have a 22' toro walk behind with wash out that works fine. Am I doing something wrong???