A network with no loops
Pipes is a rotation puzzle. You never move a tile. You only turn it, so every tile's shape is fixed and only its direction is unknown. There are five shapes: straights, bends, T-junctions, crosses and the short pipes that end at a house. The finished network is one tree spreading out from the pump in the middle. Every tile is joined to the pump by exactly one route, and the pipes never close into a ring.
That last point is a real tool. If turning a tile would close a loop, that direction is wrong. It also means every house is a dead end of the tree. A house can only face a tile that leads back toward the pump.
Start at the border
The middle of the board has the most freedom, so leave it for last. Edges and corners are the opposite. No pipe may point off the board, which rules out directions straight away.
- A bend in a corner has only one legal direction. Its two ends must face the two neighbours inside the board.
- A straight on an edge must run along that edge. The other direction would point off the board.
- A T-junction on an edge must turn its closed side to the wall. That leaves one direction: along the edge both ways, and inward.
- A house on an edge has at most three directions, and usually fewer once its neighbours are known.
Each tile you settle tells its neighbours something. If a fixed tile has an end facing right, the tile to its right must have an end facing back. If it has no end facing right, the tile to its right must not point at it. Work around the border this way, then step inward one ring at a time.
Here is a short example on the 5×5 board. Say the top-left corner holds a bend. It must open to the right and down. The tile to its right is a straight, so it must lie along the top edge. Now the third tile in the top row has a pipe coming in from its left. If it is a house, it faces left and is done. If it is a bend, it must turn down, since the top edge is closed. Three tiles are settled, and you haven't guessed once.
Use the lock as a promise
Holding a tile, right-clicking it, or pressing L locks it. The padlock is just your note, and it doesn't count toward the win. But it stops stray taps, and it shows at a glance which tiles you have proved. Lock a tile only when you are sure. A wrongly locked tile blocks the solution, and it is easy to stop questioning it.
Habits that waste rotations
- Starting from the pump. Following the water outward feels natural, but the centre has the most options. You'll turn tiles many times while the border could have told you the answer.
- Spinning to see what fits. Each tap is a quarter turn clockwise. A tile that needs a quarter turn back costs three taps. Work out the direction first, then tap the right number of times. Par counts the fewest taps from the deal to the solution, so this is how you get close to it.
- Tapping crosses. A cross looks the same in every direction, so taps on it are ignored. Straights have only two looks, so a straight never needs more than one tap.
- Trusting the water alone. Water reaching a house doesn't make that branch right. A loop or an open end elsewhere can still be hiding the real route.
Moving up in size
Easy is a 5×5 plot, Medium is 7×7 and Hard is 9×9. The rules never change, but bigger plots have longer chains of reasoning between the border and the centre. Try Easy until you can solve without spinning tiles to test them. Then move up and aim for par. Undo has no limit. Hint turns one wrong tile into place and locks it, but a hinted solve doesn't count for best times.
