I recently replaced the hoses and cleared the vent hose to the holding tank on my 1988 Cat 30. I thought the tank was leaking, but it was a clogged vent. Perhaps the pumping was causing a leak from a weak connection. The Groco head is now allowing liquid to pass through without pumping. I called Groco and they said that was OK. I suspect there is something wrong with a valve, however. The boat is still on the hard, so there is no raw water coming to the head. Has anyone had this situation? Any responses will be appreciated. Thanks...John