How to Play Water Sort: Rules, the Pouring Trap, and How to Unstick a Board
Water sort is the puzzle with the rows of part-filled tubes. The goal is simple to state—end with every tube either empty or holding a single color—and the reason people get stuck is almost never the goal. It is the pouring rule.
This guide explains the rule precisely, shows the trap it creates, and gives you a way to look at a board that makes most levels solvable on sight.
▶ Play Cozy Sort — free, no download
What water sort actually is
You get a set of tubes. Each holds up to four units of liquid, stacked. Colors start mixed across tubes, and you win when each color sits together in one tube.
You never pick a unit out of the middle. You pour from the top of one tube onto the top of another, and the pour is only legal if the receiving tube is empty or its top unit is the same color. That single restriction is the whole game.
The rule people miss: pours move a whole run
When you pour, every same-colored unit stacked on top moves together—as much as fits. Three blues on top of a tube pour as three, not one, provided the destination has room.
This is what makes empty tubes so valuable and so easy to waste. Dumping a single unit into your only empty tube spends the board's most flexible resource to move the smallest possible amount. Nearly every stall traces back to that move.
How to read a board before touching it
- Count your empty tubes first. That number is your working memory. With two you can maneuver; with zero you can only make pours that already match.
- Find colors that are already stacked in a run of two or three. Those are cheap to consolidate and should move before anything else.
- Look for a color scattered across four different tubes. That one is the puzzle. Plan where it will end up before you spend an empty tube elsewhere.
- Prefer a pour that empties a tube completely over a pour that merely tidies one. Freeing a tube gives back options; tidying gives back nothing.
When you are stuck
Being stuck usually means every legal pour makes things worse. Undo is the correct response, not restart—walk back three or four moves and look for the point where you filled an empty tube with a single unit.
If no pour is legal at all, the board is deadlocked and only undo or restart will help. In our version this never means the level was impossible: boards are generated by working backwards from a solved state, so a solution always exists.
About our version
Cozy Sort runs in the browser on phone or desktop, with no install and no account. Every level is constructed in reverse from a finished board and then checked by a solver, so there are no unsolvable boards and no fake difficulty.
Undo is unlimited, there is no move counter punishing experimentation, no timer, and no ad interrupting a level. The whole game is a few dozen kilobytes, so it opens immediately even on a slow connection.
Frequently asked
Is water sort puzzle free to play?
On Frogame, yes—Cozy Sort is free in the browser with no download, no account, and no ads interrupting a level.
Why can't I pour this color?
A pour is legal only into an empty tube, or onto a tube whose top unit is the same color and that still has room. If both fail, the pour is blocked.
Can a water sort level be impossible?
Not in our version. Levels are built backwards from a solved board and verified, so every level has a solution. A deadlock means your move order went wrong—undo, don't restart.
What is the fastest way to improve?
Stop pouring single units into empty tubes. Protecting empty tubes is the difference between clearing a board and stalling three moves from the end.
