Only got to level 5 before I couldn't take much more, haha. When I saw it I thought it'd be a nice simple game where you just join the pipes, then I find out I have to switch 5 pipes at a time! At least I only had to get to the end, for a while I thought I had to stop the liquid spilling out as well, after the end. It's a really cool concept, but I feel it should be introduced more gradually with earlier simpler puzzles.
And I don't know why I'd suggest making this harder, lol, but something I was thinking while playing was that maybe the liquid could speed up the less pipes it's got to fill? Like, if it hits a dead end early, it fills faster elsewhere. So it's like a fixed amount of water entering the whole system.
Really cool game!