On my 310 the line going from the shower sump to the pump does not seem to empty out. I can hear the pump running and checked the diverter switch between the ice box drain and the shower sump with no change (and yes the hull valve was open). Is it common for this hose to clog up and what would be the best way to clear it? I am thinking of using compressed air or something like that from under the sink to blow backwards into the head; or is this a bad idea (e.g. messy)? Thanks Ray