Peggie,Something new happened this week-end on our C30 equipped with a Groco head.I have the habit of closing all of my all of thru-hulls whenever I leave the boat but keep them open while living on board on week-ends.On Sunday morning, I woke up to my girls complaining that the head was overflowing, it was actually filled to the rim I managed to dry pump it but then when I checked my holding tank had also been filled. (I had just pumped out Friday night and there's no way we would have filled over the week-end)This is the first time this happened on board, any ideas what would have created this? What would need to be changed? Can an overfilling head actually drain into the holding tank without any pumping action???Thanks,GG