The Great Lakes are "no discharge"
That's true in both US and Canadian waters. If you're a transient boat visiting, all that's necessary is a "secured" system--i.e. thru-hull closed and the seacock handle either wired or removed..same for any y-valves. Or, if you have two heads and only one tank, lock the door to the head without a tank. The stories about requiring thru-hulls to be removed and glassed over are "urban legend"...so are the stories about boats being seized. It's never happened to ANYone--not even to US registered boats with removeable portapotties, which are illegal in Canada, but not in the US. In fact, no US boat equipped with one has ever even been turned back at a border crossing or by Canadian customs, much less seized. Worst case, if someone were actually caught in the act of dumping a tank or discharging directly overboard, the authorites MIGHT "hold the boat for ransom" till a whopping fine is paid. But they do not inspect and seize a boat because it isn't equipped to their liking.If you keep your boat on any of the Great Lakes, it doesn't matter whether you're in US or Canadian waters, y-valves and overboard discharge macerater pumps are illegal. So it would be a VERY good idea to remove all plumbing etc that could easily be connected to a thru-hull. The only setup that's legal is a head plumbed directly to a holding tank...tank plumbed only to pumpout deck fitting. But don't worry about going into Canadian waters...the Canadians are very hospitable folks who ask only that you don't pollute their waters. They do tend to get a little testy about that.And you can take all this to the bank, btw.