How does a dual flush toilet work?
Dual Flush is an interactive water saving design for a toilet. It is created with the internal flush valve allowing two separate flushing volumes for disposing waste. This type of cistern gives you the choice between a half flush for disposing liquid waste or a full flush for disposing solid waste.
Dual flush toilets handle solid and liquid waste differently from standard American style toilets, giving the user a choice of flushes. It’s an interactive toilet design that helps conserve water that has caught on quickly in countries where water is in short supply, like Australia, and in areas where water supply and treatment facilities are older or overtaxed. The Environmental Protection Agency (EPA) reports that by the year 2013, an estimated 36 states will experience water shortages as a result of increased water usage and inefficient water management from aging regional infrastructures. Using less water to flush liquid waste makes sense, but in the United States there may be cultural biases that make accepting a more hands-on approach to personal waste harder to accept
Dual flush toilet mechanism operation
For a time, toilets were called necessaries, one in a long line of euphemisms used to describe the business end of handling a simple biological process. One problem is that bodily waste is a delicate topic, so delicate that culture can be as much a factor in affecting change as necessity. Consider the words: defecate, poop and pee. They’re not accepted in polite conversation, are they? We keep our bodily functions under wraps, so any changes in our approach to handling them can create culture shock and resistance.
Imagine being in charge of a household that relied on the safe and familiar use of the family outhouse. Now, consider the reaction you may have had when the outhouse moved indoors. Walking the privies, another euphemism for going to the outhouse, might have seemed a more sanitary option than moving personal waste management into your home, yet the bathroom still made its way inside.
Dual flush toilets may be another defining moment in the development of the American john: the introduction of environmental conservation to the process of elimination. Interest in low flow and dual flush toilets is on the rise in the United States, due in part to increased government regulation and the rising cost of water, and there are incentives for making changes in the way we use the commode. In the next sections, we’ll see why change may be a good thing, learn more about the specifics of the dual flush and find out how government and business are coming together to help America flush responsibly.
There are currently two different types of dual flush valves which you can install. Firstly there is a toilet syphon which is operated by a toilet handle (For more information on how a dual flush syphon works, check out our article How a Dual Flush Syphon Works.), or a dual flush drop valve which can be operated by either a lever handle or a push button.
How much water are you wasting?
Thanks to a factsheet from Waterwise we have the following water usage data:
As you can see flushing your toilet uses more water than any other household item totaling to 30% of all consumed water.
How much water would I save with a half flush?
Most toilets have a flush volume of 6 litres and half flush of only 3. This means that each half flush would save 3 litres of water. To put this into perspective, each half flush will save more than your recommended daily intake of water! This could equate to a massive saving of 24 litres (over 40 pints) of water per person each day, and of course, a massive saving on your water bills.
Dual-flush toilets can save water. The idea is that the controls provide just enough water to do the job, using a small volume of water for urine and possibly a little paper, and more water to flush away solid waste and ensure that the bowl is cleaned. They were common for several years in Europe before they started appearing in the U.S.
Below is a picture of a public toilet equipped with a dual-function handle, explained by an accompanying sign. The idea is that you lift the flush handle upward for a small-volume flush for liquid waste and push it down for a large-volume flush for solid waste (termed “#1” and “#2” just like in kindergarten).
A further innovation seen here is an anti-bacterial handle. The sign mentions that the flush handle is coated to protect against germs. The metal lever is covered with a green plastic coating which has been permeated with anti-baterial chemicals.
Dual-flush toilets are available, but you can convert an existing toilet to dual-flush operation.
Here are several conversion kits available through Amazon.
What you frequently find in European settings is a button on the top of the tank. Looking closer, you see that the button is split. Press the smaller segment to produce a smaller flush, press the larger segment and both parts move, producing a larger flush. Here are two examples from France.
What Happens when a Toilet is Flushed: 3 Basic Operations
- Flushing the toilet opens the flush valve: A flush lever moves an arm to lift a flapper valve or tank ball to permit water to rush into the toilet bowl below, washing away waste into the sewer pipe. [Other toilets may use a siphon-flush valve to activate the flush cycle. At the end of the flush cycle, a float arm, or a float moving on a vertical stalk (newer valves) drops to open a valve permitting the toilet tank to refill with water.
- Re-Filling the Toilet Cistern or Tank: When the toilet tank water level reaches the proper level, the float closes the toilet tank fill valve.
- Additional Water Enters the Toilet Bowl: during the re-filling of the cistern or toilet tank, as long as the toilet fill valve is open to allow water to enter the toilet, most designs use a small diameter tube to direct a portion of the incoming water down the cistern tank overflow tube (see sketch above) and into the toilet bowl. This extra water helps assure a proper level of water in the toilet bowl to prepare it for its next use.
Dual flush toilets handle solid and liquid waste differently from standard American style toilets, giving the user a choice of flushes. It’s an interactive toilet design that helps conserve water that has caught on quickly in countries where water is in short supply, experience water shortages as a result of increased water usage and inefficient water management from aging regional infrastructures. Using less water to flush liquid waste makes sense, but in the United States there may be cultural biases that make accepting a more hands-on approach to personal waste harder to accept .
The flap valve system was relatively simple; the operation of the lever caused a valve in the bottom of the cistern to open, allowing water to flow down into the bowl.
Both types used a ball-cock system to maintain the water levels in the cisterns and a lever on the side of the cistern to operate the flush mechanism.
Read more:”How much water is used when you flush the toilet“