Using a variety of pipe pieces presented randomly in a queue, the player must construct a path from the start piece for the onrushing sewer slime, or "flooz", which begins flowing after a time delay from the start of the round. Pieces may not be rotated; they must be placed as presented in the queue. The player can replace a previously laid piece by clicking on it, as long as the flooz has not yet reached it; however, doing so causes a short time delay before the next piece can be laid. The flooz is required to pass through a given number of pipe pieces in order for the player to continue to the next round. Some rounds also include an end piece, which must be the end of the pipeline the player has constructed, in addition to fulfilling the minimum pipe length requirement.
Completing the sewer pipeline in the time allotted allows the player to advance to the next level, which means a shorter interval from the start of the round until the flooz starts flowing, as well as faster-flowing flooz. On higher levels, some special pipe pieces appear in the game, such as reservoirs, one-way sections, and bonus sections. Obstacles and wrap-around sections also appear on the game board on higher levels.