this past season I have had problems with the head flushing. I have the holding tank emptied and it still acts as if it is full and runs out the deck outlet (not all the time but more often than note). I have tried running thewater hoseat high pressure down into the tank when it is empty but the water backs out of the tank. It will run into the tank at very low pressure. Speaking with a fellow Catalina Owner, I have determined that the vent may be plugged. I can see where the vent hose hooks into the holding tank but can't see any possible way to get both hands into the small space to remove the hose clamp. Seems to only solution is to remove the tank. I tried running water at high pressure thru the vent on the outside but assume there is some type of valve in there that prevents anything entering from outside the boat. Any suggestions on unplugging the vent without removing the hose?