Richard Gleaves and Scott Hillstrom

| Instructional Objective | Learners & Context | Object of Game | Game Materials |

| Time Required | Rules | Design Process | References |

Instructional Objective

Flush! is a board game designed to reinforce learners' knowledge of how the San Diego City wastewater treatment system works. It is intended to be played after learners have been introduced to the instructional content during a field trip or class presentation.

Learners & Context of Use

Flush! is designed for students ages 12 and up who are participating in San Diego wastewater treatment educational programs.

It is specifically designed to appeal to the adolescent interest in taboo subjects such as bodily waste. This interest is reflected in the series of popular children's books and CD-ROMs collectively titled "Grossology", which teach science and health by focusing on unmentionable bodily secretions, and whose success justifies the approach taken here.

Flush! is intended for classroom use. Because it supports only up to 3 players, a number of game copies would need to be available to allow all students to participate.

The game is designed to be played in 30 minutes to fit within typical classroom time constraints. The setup time and game rules are consequently minimal.

Object of the Game

Be the first to move your pieces through the sewer line and treatment plant. Move through the sewer line by rolling a die. Move through the treatment plant by correctly answering questions about wastewater treatment.

Number of Players


Game Materials

Game Board

Sample Cards

Time Required

Flush! takes about 30 minutes to play. The setup time is less than a minute.


  1. Open the box, take out the game board, and put it on a flat, even surface.
  2. Stack the Sewer Cards on the space labeled "Sewer Cards" on the board.
  3. Stack the Treatment Cards on the space labeled "Treatment Cards" on the board.
  4. Each player chooses 3 pieces of the same color and puts them in one of the toilets on the board.

The Rules

  1. Each player rolls the die. The highest score determines who goes first. (If two people roll the same value, they roll again.) Players take turns in clockwise order.

  2. Players take turns by rolling the die and moving one of their pieces the corresponding number of spaces through the sewer line.

  3. If you land on a Sewer Card space, ask another player to draw the topmost Sewer Card and read it out loud. You must do what the card says. The other player returns the card to the bottom of the Sewer Card stack.

  4. When a piece enters the treatment plant it always stops in the first circle. You don't have to roll an exact number to enter the plant.

  5. To move a piece that's in the treatment plant, ask another player to draw the topmost Treatment Card and read it out loud. If you answer the question correctly, you can move the piece to the next circle in the plant. The other player returns the card to the bottom of the Treatment Card stack.

  6. The first player to move all their pieces through the treatment plant wins.

Design Process

After entertaining two ideas for highly unconventional educational games, I (RG) decided to minimize the project risk and instead create a board game using one of the traditional formats described in Ellington, Addinall, and Percival (1982). I focused on the race-track format because of its simplicity and ubiquity.

Initial Idea

To compensate for my timidity in choosing a game format, I made a conscious effort to come up with unconventional gaming content. The idea of a sewer system came to mind. I immediately liked it for a number of reasons:

The value of such a good game-to-content fit is made clear in Ellington et al. (1982): "Provided that the educational content and game structure are well integrated they can again form the basis of an educational or training exercise in which the participants are highly motivated."(p. 48)

Thus the initial game idea consisted simply of a race track path superimposed on a map of San Diego, with the start of the race marked by drawings of one or more toilets.

Content Research

The next step was to research the content. A visit to the SDSU library yielded mostly World War II era books on sewage treatment. Talking to employees at local gaming emporia (Game Empire, Game Towne, and the PBS Store of Knowledge) revealed, unsurprisingly, a dearth of educational board games on the subject of sewage treatment (though I was referred by a Game Empire employee to the popular children's books collectively titled "Grossology", which teach science and health by focusing on unmentionable bodily secretions, and whose success validates the educational approach used here.)

The breakthrough came when Bernie recommended that I contact the City of San Diego to obtain literature on the sewage system. I did so, and discovered that public relations people at the Metropolitan Wastewater Department (MWD) are prompt, friendly, and in possession of extensive and well-produced literature describing the sewer system and sewage treatment process. As a bonus I learned that the MWD is coordinating with a local environment group (Think Earth) to present outreach programs to local schools teaching how the sewage system works; when I told them about the game idea, they sent the relevant literature immediately and asked that they have a chance to see the finished product.

The literature immediately revealed two things: 1) "wastewater" is the preferred term over "sewage"; 2) most of the learning content associated with the wastewater treatment system has to do with what happens at the Point Loma treatment plant, not in the sewer line itself. From a gaming point of view, this meant that the race track itself did not correspond with the bulk of the content to be learned. This problem was solved by dividing the race track into two distinct parts:

  1. The sewer line (which comprises most of the race track).

  2. The treatment plant (a series of three spaces at the end of the sewer line which are drawn to represent a diagrammatic treatment plant). Most of the learning content is presented as game pieces move through this section.

Game Context

The school program provided a well-defined educational context within which game design could proceed:

The limited playing time drove many aspects of the game design. First and foremost, the game had to be as simple and self-explanatory as possible - its goal would be to present the learning content with minimal gaming overhead. Second, the game itself had to be designed to be playable within the specified time limits - this was achieved by estimating the average amount of time necessary per player turn and then designing the game around this.

Game Overview

About this time Scott Hillstrom joined up with me to work on the project.

The design evolved so the players would move their pieces relatively quickly through the sewer line while spending comparatively more game time moving through the treatment plant. This is a direct analog with the real-life system being modeled; it also provides more opportunities for presenting the sewage treatment process content at the appropriate part of the game (i.e., while the game pieces are in the treatment plant).

We decided that player pieces would be advanced through the sewer line by the roll of a die, but that advancement through the treatment plant would be controlled by answering questions related to the treatment plant. This suggested the use of cards, which became known as "treatment cards". To simplify the transition of pieces moving from sewer line to treatment plant, the rules were designed to allow pieces to move into the first space of the plant (but no further) without having to roll the exact number of spaces. In other words, if your piece was two spaces away from the plant and you rolled a six, you could move the piece to the first space in the treatment plant.

We also added the caption "Roll die to advance" to the beginning of the sewer line. Since this parallels the "Draw Treatment Card to advance" caption that appears next to the treatment plant, it is meant to serve as a subtle reminder that a die roll will not advance you through the treatment plant.


To add some interest to the sewer line, and to present the small amount of learning content associated with the sewer line, two of the sewer line spaces were specially marked as requiring a "sewer card" to be drawn. These cards would either advance the piece forward or delay it. The initial decision was that a positive sewer card outcome would allow the user to roll again, while a negative outcome would cause the player to lose a turn. Game testing revealed that this design feature caused two distinct problems:

  1. It was easy to forget whether a player had lost a turn or not the next time it was their turn.

  2. The ability to roll again after a successful card set up a behavioral schema in the sewer line part of the game which clashed with the schema for advancing through the treatment plant. That is, we found ourselves accidentally taking multiple turns per player in the treatment plant after correctly answering treatment cards, because earlier in the game a positive sewer card outcome had allowed players to take multiple turns.

To fix these problems, we changed the sewer card outcomes from the loss/gain of a turn to the loss/gain of a space. This could be executed immediately, with no need to remember whether a given player had lost a turn, and no option to roll again and thus take a multiple turn.

Board Layout

After reviewing the provided map of all the sewer mains in San Diego, we decided to model the real-life sewer line that runs through Mission Valley down to Ocean Beach and then south along the coast to the Point Loma treatment plant. This allowed the inclusion of Mission Bay and San Diego Bay as recognizable map landmarks. The San Diego freeway system is drawn in to provide an orientational framework for the rest of the map. Initially we wanted to show both QUALCOMM stadium and Sea World as the only two non-bay non-freeway landmarks; however, one of the toilets ended up on the stadium site, so only Sea World remained. (Note the semantic connection between Sea World and an effective wastewater treatment system.)

Scott suggested a slight deviation of the sewer path to make the game path more interesting. Instead of two straight lines and a dogleg, the game path now includes a series of slight curves as it passes Mission Bay. These curves provided natural places for the unpredictable Sewer Card spaces to linger near (an allusion to a known property of nonmetaphoric race tracks).

The toilets that serve as the start of the game path are connected to the central path by their own paths, thus echoing the real-life connection of local pipes to the neighborhood sewer main.

The Sewer and Treatment Cards are placed on the board adjacently to their corresponding structures, thus minimizing confusion about what card stack to draw from. The cards are also color-coded with their corresponding structures.

Board size constraints prevented us from modeling the outfall pipe which runs four miles out into the sea from the Point Loma treatment plant. Thus game pieces move directly from the treatment plant into the adjacent ocean. To mitigate this deviation from reality, we used the graphic trick of aligning the word "Finish" to appear in the same position as the outfall pipe. Thus even though the pipe is not part of the game path, its presence is suggested. (The outfall pipe is part of the content to be learned.)

Finally, plenty of board space is left unused for die-rolling room.


The sewer line is colored a light brown to suggest sewage. The Sewer Card spaces are colored yellow to stand out. This same yellow is used on the Sewer Cards themselves. Spaces in the treatment plant are colored light blue to suggest that the sewage is being transformed to clean water. The same light blue is used on the Treatment Cards.

The game pieces appear in neutral basic colors: green, yellow, and red. We decided against using content-suggestive colors such as brown because of the negative connotations of allowing such pieces to move into the ocean after passing through the treatment plant.

Game Pieces

Each player is assigned multiple game pieces. This has both gaming and content value. Having multiple pieces moving through the sewer system more accurately represents how the system works. From a gaming perspective, having multiple pieces offers players a choice of which piece they wish to move, giving them more control over whether or not they land on a Sewer Card.

The game pieces consist of small colorful hard candies cut in half to provide a flat nonrolling surface and coated with nontoxic Elmer's glue to eliminate the sticky factor. Should a student decide to eat one of their pieces, they will be unable to finish the game -- a suitable negative incentive. Furthermore, the more perceptive players may realize that the eaten piece will still end up traversing a sewer system.

Game Duration

We estimated (by experimenting) that a single turn in the game would take an average of 30 seconds. This implies a total of approximately 60 moves to complete the game. Based on this number we chose the following number of players, sewer line spaces, and game pieces:

3 players x 3 pieces x ((10 sewer spaces / average roll of 2.5) + 3 treatment spaces) = 63 moves (versus the 60 estimated moves)

The average roll value of 2.5 is achieved by using a single four-sided die. (Probability calculation: 1+2+3+4 / 4 = 2.5)

Card Protocol

We designed the rules so that when a card is drawn, it is not done by the player taking the turn, but by one of the other players, who must read the card out loud. This presents the content to all learners, not just the one taking the turn. It also raises the involvement level of all players.

The Treatment Cards will be drawn at least 27 times in a game with 3 players:

3 players x 3 pieces x 3 treatment spaces = 27 card draws

Because there are only 18 Treatment Cards, they are guaranteed to be at least partially recycled during the course of a game. This repetition offers players a chance to remember the answer from a card's last presentation, thus increasing his or her chance of advancing.

Game Testing

Playing the game revealed the design problems described above in the "Obstacles" section.

We also altered the relative mix of positive and negative Sewer Cards. We had initially decided to make the odds 50/50 that a player would draw a positive Sewer Card. In practice, this (combined with how randomness actually works in small data sets) caused the Sewer Cards to seem uniformly negative and thus something to be avoided. Since the Sewer Cards contain relevant learning content, the odds for drawing a positive Sewer Card were changed to 75/25. However, since it is the negative cards that contain the most important content, the cards should be arranged to ensure that the most important negative cards appear near the top of the Sewer Card stack to ensure their presentation. This represents an interesting case of gaming/learning interaction -- a card order that appears to be random from a gaming point of view may in fact be carefully sequenced for learning value.

Ideas Rejected

Production Quality

We produced Flush! at a higher-than-specified quality level for three reasons:

  1. Scott has the tools and skills for producing computer-based output quickly and easily.

  2. We will be presenting the finished game to the MWD for possible inclusion in their educational program.

  3. We saved design and test time by ruthlessly simplifying the board elements and rules beforehand, leaving more time to work on esthetic details.


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Last updated October 22 1998