This is my first guide on Steam, I have some others up at GameFAQs on another name, but meh.

These two puzzles were requested in multiple threads in the discussion I saw, and were also the ones my lovely parents struggled the most with. On top of that, the valve puzzle doesn't dish out a hint but simply the solution. UNACCEPTABLE!
Which is also the problem when you would Google for a hint, you stumble upon a solution way faster. So for those that don't want to rob themselves of the pleasure of solving, some step-by-step logic so you can cheat only as much as you need.

If you'd like to see another one up here, drop a PM. Or whatever Steam calls them.

The valve puzzle:

Goal:
To place valves on five of the ten joints, blocking that pipe, so that none of the waterflow from the bottom-left spout can reach either of the two spouts on the right.




Hints:
1. The goal is actually to divide up the pipes into two parts, a "wet" and a "dry" part.
2. The valves are on the border inbetween the wet and dry part.
3. Take a screenshot and open your image in paint to draw more easily and directly.
4. Draw what is certainly "wet", starting from the bottom-left spout.
5. Progress:

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6. The joints that have "wet pipe" on both sides certainly don't need a valve on them.
7. Do the same, tracing the "dry" from the right pipes.
8. Progress:

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9. The joints that have "dry pipe" on both sides certainly don't need a valve on them.
10. The other 5 joints are where you need to put the valves.

The boat puzzle:

Goal:
Connect all four pairs of boats of the same color by a line. Lines of different colors may not intersect, nor share any crossroads.
Note:
There is a bug where the yellow boats will incorrectly registers as paired sometimes.

Hints:
1. Start with the yellow boats.
2. The yellow boats are on the edges, if the line would go directly through the middle it would cut all the other paths, so it needs to go all the way around up or down.
3. Let's say that the yellow path is like this.
Is it possible to solve the puzzle like this? Why?
4. The top blue boat is completely cornered, so it has to go straight to the other blue boat. But this leaves a 1-wide space for both red and green to go through. So we've made a false assumption.
5. The false assumption is that the yellow boat went up. We now try the other way, that the yellow boat went down.
6. If the blue boat were connected around the red and green boat, the red and green path would have to cross. This is wrong.
7. So it has to connect directly.
8. Solution.