when I look at the boxes and press / p a message appears "You´ve not got enough pipes to build that i´m afraid."
What am I doing wrong.

You need to configure the permission levels and then assign them to users or groups.

{
  ...
  "xmasLights": false,
  "permLevels": {
//      "newLevel":{
//          "upgradeLimit": 0 - twigs, 1 - Wood, 2 - stone, 3 - metal, 4 - high quality, -1 - unlimited (high quality)
//          "pipeLimit": -1 - unlimited, or the number of pipes that can be built
//      },
      "level1": {
      	"upgradeLimit": 1,	// This allows pipes to be upgraded to wood.
      	"pipeLimit": 25     // This allows the player a maximum of 25 pipes.
      },
      "level2": {
      	"upgradeLimit": -1, // This allows pipes to be upgraded all the way to high quality metal.
      	"pipeLimit": -1		// This allows the player to build an unlimited number of pipes.
      }
  }
}​

Thanks