Groco HF head

[bhstech]

I have a 86 Catalina 27 that I just bought a few months ago. The head uses sea water for flushing and into a holding tank. About 5 weeks ago, on a long passage, the head was used several times. A week or so after, I noticed a smell from the head. I found the bowl full of some foul matter. I flushed it and assumed someone didn't know how to operate the head. I pumped the bowl dry. A few days ago I happened to look into the head and found greenish water in the bowl. Didn't really smell. Again I flushed and pumped dry. As far as I know no one had used the head. Today I looked again, and the green was back and I flushed and pumped dry. What is going on? I assumed the holding tank was empty when I bought the boat. I was told it was and the PO didn't use it(the boat or the head) all that much over the last few years. Could the tank be full? Is a check valve leaking?

[HopCar]

The green water that doesn't smell bad might be sea water that is flowing into the toilet if it is mounted at or below the waterline. The cure is to set the little lever on the side of the pump to the horizontal position. This closes the inlet valve.

From the toilets instructions:

Close the valve handle (horizontal)
when flushing is complete. You will
hear the valve

click closed.

Warning: Failure to close the

valve could flood the toilet.

"Could the tank be full?" Of course it could be full.

[bhstech]

Went to the boat today and the bowl was full again. But I had left the lever up (Duh!). Put it horizontal, pumped it dry and went sailing. After 2 hours or so of a very nice sail, and it was still, mostly empty. I went into the V berth and looked at the seacock under the hatch and saw that there are 2 seacocks. One is the drain to the sink and the other is attached to the macerator. (is that legal?) It was way too hot to spend too much time in there so I closed the macerator seacock. the other is open for the sink drain and I think it is also attached to the suction hose to draw water from the lake into the head to flush it.
Could this have been the problem all along?
I plan to go to the boat again some time this week in the morning when its cool enough to really check it out.