This year was the time, to replace that fitting. It was very difficult to get at, being close to the side of the hull, and I didn't want to take the whole tank out to replace it. So I came up with this idea.
|Diassembled vent and mounting disk.
The old vent hole was closed off using a plug they use on hydraulic items. I had one come off a new transmission cooler that was the right size. And of course to keep it in there, I used my favorite product, 3M 4200. One day the tank may be removed and that will be the time to remove the old brass fitting epoxied into the tank.
You might notice the inlet to the holding tank is also on the side, (under the old vent line). I don't under stand why they were built that way. Both the vent and the inlet should be on the highest point of the tank. Next year, I might move the inlet to the top of the tank. And that will give me a couple of more flushes. Doesn't a flush beat a full house?