How a Flush Toilet Works

Until recently, gravity flush toilets were the most common types of toilets found in residences. In public restrooms, commercial buildings and apartments, we had the tankless Flushometer type operated toilets. But today, water conservation is the driving force behind a search for the most efficient flushing toilet, and we now have a variety of mechanisms operating our toilets. While the designs may vary considerably, the basic operation of a toilet is to have water that is stored in a tank above the bowl to clean the bowl of waste using the minimum amount of water.

Early gravity flush toilets used a tank that was mounted on the wall above the bowl and the user pulled a chain to release the water into the bowl. The weight and the pull of gravity permitted the water to clean and clear the bowl of wastes. With improvements in the tank and bowl, the tank was moved down to sit on top of the bowl and in some cases even appears to be almost level with the bowl or an integral part of the bowl.

According to Flex Your Power’s website, "The United States uses about 5.8 billion gallons of water every day to flush waste." They report that toilets and urinals account for nearly one-third of building water consumption. Today, some toilets are so well-engineered they can flush solid waste with just 1.4 gallons of water per flush rather than 3.5 to 7 gallons of water used by older designs. The industry standard is 1.6 gallons of water. There are newer designs that pressurize the water inside a container in the toilet tank.

"Not uncommon in the United States, this system (invented by Bruce Martin) uses the water pressure within a structure to compress air within a closed vessel located within the vitreous enclosure. When flushed, the compressed air pushes into the bowl at a velocity (flow rate in gallons per minute or liters per second) significantly higher than gravity flow. This system is more water efficient than a tank type and can be installed into the same fittings as the latter. However, it costs 10% less than the new 3" (75 mm) gravity flapper equipped tank-type toilets.

Pressure assisted toilets are used in both private (single and multiple and lodging) bathrooms as well as light commercial installations (offices, etc.) They hardly ever clog and so require less maintenance, but tend to be noisier - a concern for residential settings." While gravity toilets will work with very low water pressure from the water supply system, the newer pressurized low-flow toilets need a minimum of 20-25 psi of pressure at the toilet to operate.

What is a Standard Toilet?

There are two toilet bowl rim sizes in the world that are considered "standard". The small one is called "round" and the larger is called "elongated". The only other variant from this is the height of the toilet. Most toilets are between 14 and 16-inches from the floor. The other height that is available is called handicap or ADA compliant height. This height is mandatory for handicap toilets in the U.S. (Mandated in the American Disabilities Act or ADA). The height of this toilet is between 16 ˝-inches and 18-inches.

The typical rough-in dimensions of a toilet is a measurement from the back of the toilet to the center of the waste outlet hole on the underside of the toilet bowl. Or put another way, the distance from the wall to the two bolts on either side of the toilet bowl. The most common dimension today is 12-inches, but in older homes 14-inches were common. But many toilet manufacturers also offer two other sizes in case mistakes are made during construction or a pesky floor joist gets in the way. It is not unusual to find toilets with a 10 or 14 inch rough-in dimension. Be sure you purchase a toilet bowl that has the correct rough-in dimension to match your current drainage pipe location.

Dual Flush Toilets

A concept that has gained a lot of enthusiasm is the toilet that gives a user a choice when flushing. Available in Europe and other countries outside of the U.S. for many years; they are mandatory in all new toilets in Israel. Dual-flush toilet technology allows the user to select a short flush (three liters) or long flush (six liters) depending on whether there are liquids or solids in the bowl. The Canada Mortgage and Housing Corporation (CMHC), in partnership with 12 municipalities across Canada, conducted a pilot program to test dual-flush toilet technology in residential, commercial and institutional settings.

The CMHC conclusion after studying 70 toilets is that dual-flush toilets perform well in comparison to 6-litre and 13-litre toilets based on water consumption rates, saving an average of approximately 26 per cent more water than single-flush 6-litre toilets. Duel flush technology is available in a wide range of toilets from the home center varieties to the upscale European-inspired one-piece ceramic toilets.

This Italian-inspired Wasauna one-piece toilet is another example of a toilet that uses the Dual Flush Technology. One button activates a 3-liter (0.8 gallon) flush while the other releases the full 6 liters (1.6 gallons). It uses a jet flushing action, with ample water surface and the glazed trapway to help prevent clogging.

"High-tech" toilets

Advanced technology is being integrated into toilets with more and more functions, especially in Japan. By far the largest toilet manufacturer in the world, producing over 7 million toilets annually, is TOTO in Kitakyushu, Fukuoka Prefecture, Japan. Such toilets can cost from US$2,000 to $4,000. The features are operated by control pads (sometimes with bilingual labels), and even hand-held remote control devices. Some of these features are: Water jets, or "bottom washers" like a bidet, as an alternative to toilet paper; The "Washlet," Toto's portable hand-held bottom washer ; Blow dryers, to dry the body after use of water jets ; Artificial flush sounds, to mask noises such as body functions ; Urine and stool analysis, for medical monitoring. Matsushita's "Smart Toilet" checks blood pressure, temperature, and blood sugar. ; Digital clock, to monitor time spent in the bathroom; Automatic lid operation, to open and close the lid; Heated seats; and Deodorizing fans. From Wikipedia, The free online encyclopedia.

Understanding how the simplest toilet works

A gravity-flush toilet is a relatively simple fixture, but it depends on numerous parts all working together. When one part breaks down, the whole apparatus malfunctions. Here's how the chain of events should work...

The toilet tank is attached to the water supply through a thin pipe under the tank. That pipe connects to the bottom of a refill valve (ballcock). The refill valve has a float to control the water flow into the tank which is usually found on the left side of the tank.

In the center of the tank at the bottom is a large hole that leads to the rim of the toilet bowl with a stopper that plugs the hole and prevents the water from flowing into the bowl. The stopper is attached to a chain that in turn is connected to the handle of the tank. When the handle is turned or pushed, it lifts the stopper out of the hole and allows the water stored in the tank to quickly run into the rim of the bowl. As the water level in the tank falls, the float control on the refill valve drops and turns the water on to refill the tank.

Once the water in the tank drops to a predetermined level within the tank, usually set by a fixed or adjustable orifice in the flapper (stopper) or by an adjustable float on the flushing rod or chain, the flapper (stopper) falls back into the drain hole and the tank begins to refill. There will usually be at least an inch of water left in the tank, when the tank begins to refill. The float on the refill valve rises with the water and when it reaches its top shuts the water off. The water level should stop about a half-inch from the top of the overflow tube. There should be no water dripping into the overflow from the refill tube and the toilet should be silent.