How Dual Flush Toilets Function

Key Highlights

Dual flush toilets provide distinct flushing options for solid and liquid waste, offering more control over water usage. This interactive design has been embraced in water-scarce countries like Australia and regions where water infrastructure is aging or overburdened. According to the Environmental Protection Agency (EPA), by 2013, 36 states were predicted to face water shortages due to rising demand and inefficient management of water resources. Reducing water consumption for flushing liquid waste is a sensible solution, though cultural barriers in the U.S. might make this approach harder to accept [source: Safe Plumbing].

For a period, toilets were referred to as 'necessaries,' one of many euphemisms used to describe the often-sensitive subject of bodily waste. This issue arises because discussing bodily functions is a touchy matter, so much so that cultural norms play a significant role in how we address these topics. Think about the words: defecate, poop, and pee. These aren't typically used in polite conversation, right? We tend to keep our bodily functions discreet, which is why any shifts in how we manage them can lead to cultural shock and resistance.

Imagine managing a household that relied on the trusted and familiar use of an outdoor privy. Now, picture how you would have reacted when the outhouse was moved indoors. The idea of walking to the privy, another euphemism for using the outhouse, might have seemed a cleaner and safer alternative than bringing personal waste management into the home. Yet, despite any hesitation, the bathroom eventually found its way inside the house.

Dual flush toilets could represent another pivotal moment in the evolution of the American toilet: the introduction of environmental conservation into waste disposal. Interest in low-flow and dual flush toilets is growing in the United States, partly due to stricter government regulations and rising water costs. There are incentives to adjust how we use our toilets. In the upcoming sections, we'll explore why change could be beneficial, dive deeper into the workings of dual flush toilets, and see how government and industry are joining forces to encourage responsible flushing in America.

Next, let's take a deeper look into the history of the dual flush toilet and its widespread popularity across the globe.

Dual Flush Toilet Technology

Australia is credited with pioneering dual flush technology. In 1980, Bruce Thompson from Caroma Industries invented the first two-button flushing system, which allowed users to manually select the water volume for each flush—a half flush for liquid waste and a full flush for solid waste—with just the push of a button [source: Biotechnology Innovations]. The need for this innovation arose from the scarcity of water, a critical resource on a continent plagued by irregular rainfall and frequent droughts.

The concept of assessing waste and determining the most water-efficient way to dispose of it gained traction. By 1993, a redesign halved the amount of water used per flush, sparking international interest. Modern dual flush toilets now use less than one gallon (3 liters) for liquid waste and about 1.6 gallons (6 liters) for solid waste [source: Nash], a significant reduction compared to older toilets, which consumed five gallons (19 liters) or more per flush.

Today, dual flush toilets are widely used across Australia, Europe, and Asia, and they are becoming increasingly popular in other parts of the world. Factors such as greater environmental awareness, government regulations, financial incentives, and rising water costs are encouraging U.S. consumers to make the switch to dual flush and low-flow toilet designs.

So, how exactly do they work? In the next section, we will explore how dual flush toilets manage waste disposal.

How the Dual Flush Toilet Manages Waste

The amount of water used to clear waste from the bowl largely depends on the flushing mechanism. Standard toilets rely on siphoning action, where a siphon tube is filled with water to draw waste and water down the drain. Once air enters the tube, the siphon effect ends. In contrast, dual flush toilets use a larger trapway (the hole at the bottom of the bowl) and a wash-down flushing design, which pushes waste directly down the drain. Since siphoning is not involved, dual flush toilets require less water per flush. The larger trapway also facilitates easier waste removal. With the option for a half flush for liquid waste, dual flush toilets can save up to 68 percent more water than conventional low-flow toilets [source: Green Building].

Dual flush toilets feature a wider trapway, reducing clogs and using less water for efficient flushing compared to conventional toilets. However, they have their drawbacks. Dual flush models tend to be more expensive than other low-flow designs. Aesthetic preferences can also be a challenge; dual flush toilets typically retain less water in the bowl, which might make it seem less tidy. Even with a full flush, some streaking can occur, and you may need to use your toilet brush more often. On the plus side, you probably won’t need to keep a plunger around.

In the next section, we’ll explore what’s involved in installing a dual flush toilet.

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Installing a Dual Flush Toilet

Installing a dual flush toilet is very similar to installing a low-flow toilet. While hiring a professional plumber is the most convenient option, it’s also a project a DIYer can manage in an afternoon.

If you’re planning on installing the toilet yourself, there are a few things you’ll need to know. Below are some general tips to guide you, but keep in mind that dual flush toilet models can vary. Make sure to closely follow the installation instructions that come with your chosen model:

If installing a completely new toilet seems like too much, there are retrofit kits available that can convert your current toilet into a dual flush system. The bowl will still rely on the traditional siphon system to clear waste, but with the retrofit, you'll have the ability to choose between a partial flush or a full flush, helping to save water in the process.

Curious about the future of toilets in the U.S.? In the upcoming section, we’ll explore where the market is headed and how that may impact the adoption of dual flush technology.

The Future of the American Flush: High Efficiency Toilets

In 1994, the National Energy Policy Act was passed, mandating that all toilets sold in the U.S. must use no more than 1.6 gallons (6 liters) per flush [source: Green Living]. This conservation-driven policy has paved the way for high efficiency toilets (HETs), utilizing technologies such as pressure-assist, gravity flush, and dual flush to minimize water usage. Among these, dual flush stands out due to its intuitive design, allowing users to choose a low-water flush using just one gallon (3 liters) or even less, rather than the standard 1.6 gallon flush limit.

While new toilets for both new builds and renovations must adhere to updated standards, millions of older, water-thirsty toilets continue to exist. With rising water and sewer bills, low flow toilets are becoming more appealing to American consumers. In response, local and state governments are offering rebates and tax incentives to encourage households to adopt these newer, water-efficient technologies.

The benefits of low flow toilets in conserving water and reducing strain on local water treatment plants are clear. USA Today reports that the average person flushes the toilet five to eight times daily, and with older models using five gallons per flush, the water usage adds up quickly [source: Winter]. According to the Environmental Protection Agency, removing all outdated, water-wasting toilets would save the United States around 2 billion gallons of water every day [source: Green Living]. Given a growing population, aging water infrastructure, and the potential impact of global warming on weather, water conservation is more critical than ever.

Where does the dual flush toilet fit into this situation? The answer isn't clear yet. While many major toilet manufacturers are preparing to offer these water-saving toilets, it's still uncertain whether the American public will embrace a change in their bathroom habits.