Sewage Surfer Solutions
Big thanks to The Scooby Gang for allowing me to use their images :) Thanks to ThermalSweater for Level 48, 49 and 50 and thanks to Diana, aka wolfie for level 47!

Please note that these images are not a step-by-step walkthrough to the game. The pipe types are completely randomized, so the following images are a guide as to possible end results.

[Level 1] [Level 2] [Level 3]
[Level 4] [Level 5] [Level 6]
[Level 7] [Level 8] [Level 9]
[Level 10] [Level 11] [Level 12]
[Level 13] [Level 14] [Level 15]
[Level 16] [Level 17] [Level 18]
[Level 19] [Level 20] [Level 21]
[Level 22] [Level 23] [Level 24]
[Level 25] [Level 26] [Level 27]
[Level 28] [Level 29] [Level 30]
[Level 31] [Level 32] [Level 33]
[Level 34] [Level 35] [Level 36]
[Level 37] [Level 38] [Level 39]
[Level 40] [Level 41] [Level 42]
[Level 43] [Level 44] [Level 45]
[Level 46] [Level 47] [Level 48]
[Level 49] [Level 50]

Alternative methods
[Level 10]

Level 24 Note
Submitted by paintcrewchief
The pattern suggested for level 24 is incredibly more complicated that required for a good amount of neopoints. Linking just the main pipe (i.e. only horizontal pipes required) alone gets you at least 500 neopoints. It is an easier alternative.