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Basic kitchen sink design- a draining experience
By Ken Foote, Contributing Editor -- Design News, January 18, 1999
In the 10/19/98 issue of Design News, we challenged readers to tell us why the following problem cannot be solved: "When designing a kitchen sink that will be rated 'uncloggable,' how many once-a-day hairwashing teenage girls must be factored into the design?" Here's reader K. Foote's humorous take on this somewhat hairy no-problem problem.
The "uncloggable" kitchen sink dilemma presents an ideal study to contrast design engineering with engineering management. From the perspective of engineering, technical challenge represents the opportunity to improve design and thereby solve a real and present flaw in a product. Management's perspective deals with how to overcome a perceived problem in the least amount of time and money.
Design approach. In the case of the uncloggable sink, the engineer starts with a study to investigate and quantify the technical concerns, including the characteristics of hair that cause drains to clog, the standard rate of hair flow from a teenage girl washing her hair daily, and specific drain materials and configurations that offer superior resistance to clogging.
Engineering management takes a slightly different approach that deals with how best to achieve clog-free sink drainage for minimum cost and time. Their concerns include quantifying the number of clogs allowable that will still permit the sink to be rated "uncloggable," preparing a classification for kitchen sinks (no hairwashing allowed) versus bathroom sinks, and providing a disclaimer that "unauthorized" hair washing violates the manufacturer's warranty.
Review suggests that these are two completely divergent paths towards solving the "uncloggable" sink problem. But we also see that there remains one similarity: The necessity to quantify the number of once-a-day-hairwashing teenage girls that will be using the sink.
Engineering investigation. To make this determination, the engineering team would first prepare a survey of the target sink user, including demographic figures and household studies to determine the mean, median, average, and maximum quantity of teenage girls present in an average household. This value will be entered into a computer simulation along with forecasts for slumber parties, makeup parties, and dating frequency.
Second, the team would prepare a series of experiments to quantify sink drainage as a function of hair length; type; style; treatments (sprays, conditioners); and color.
Engineering management process. Management in any modern enterprise requires organization of a project task team. The team's second agenda item is to identify an engineering unit to whom the work shall be delegated. Next, identify the work to be performed by said unit, namely:
Step 1: Define the perceived problem. The realized problem here is not drain clogging, but rather improperly managed sink drainage. The engineering team must prepare options for improved sink drainage management and quantify the maximum hair-mass flow rate possible without creating a clog.
Step 2: Quantify the requirements. Any good manager knows the key to successful marketing is to identify the loopholes in specification compliance. The team quantifies the number of clogs that the sink may have, yet still qualifies for the "uncloggable" rating. This capability enables the sink to clog during infrequent peak hairwashing conditions (i.e.: slumber parties), but obviates the need for the engineering department to predict and test these peak hair loading conditions on sink drainage.
Step 3: Organize the problem's resolution. Improved sink-drainage management is achieved at minimal cost and time through the preparation of a maximum teenage-hairwashing rate. The rate for the "uncloggable" sink can be defined as the maximum ratio of hair mass to net area of the drain opening. While the flow rate of hair has a specified maximum, the number of girls can vary depending upon their individual hair characteristics.
Which leaves us with the question, "How many once-a-day-hairwashing teenage girls must be factored into the design?" to be answered.
The Purist Engineer's Perspective: Numerous factors serve to vary the number of girls that must be incorporated into the design equations for development of an "uncloggable" sink design. The number of teenage girls that must be factored into the design is the exact number present when the drain clogged in the first place.
The proof of this figure is evident through analysis using the sanity check, "To avoid clogging, the number of teenage girls must be 'one less' than the number present when the clogging situation was experienced." However, this figure will change as aging factors on the drainage system degrade its performance.
The Engineering Manager's Point of View: The number of teenage girls is "whatever number that is required to generate the maximum hair flow rate" that the sink's drain was designed to accommodate. This figure would be presented as a fixed, specific number of average teenage girls with average hair. The bottom line: Even though the sink is rated as uncloggable, whenever once-a-day-hairwashing teenage girls are around, clogging is inevitable.
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