How a Toilet Flushes: Find Out What Happens After You Flush

Many of us take our toilet for granted in ways we’d rather not discuss. When you think about the alternatives, though, a toilet is a wondrous invention. So, what’s going on in there? Learn how a toilet flushes and what happens after you walk away.

How a Toilet Flushes

There’s no power plug required for a standard toilet. Instead, gravity flushes the toilet with the help of a drain, fill valve, and other parts that keep the toilet flushing. Here’s a breakdown of how the system works.

1. Turning the Toilet Handle Moves the Flush Valve

You may have noticed the chain inside your toilet tank attached to the handle. When you turn the handle, it pulls this chain upward and lifts the flush valve. This process reveals a small drain hole.

2. Toilet Water Gets Siphoned Away

The hole at the bottom of your toilet bowl is technically referred to as a siphon jet. When you flush the toilet, water drains from the tank and enters the toilet bowl at high speeds, resulting in a siphon effect for the remaining wastewater. This effect occurs when wastewater rushes into the siphon hole and through the siphon tube.

3. Wastewater Gets Transferred

Once the wastewater in the toilet gets flushed, it flows through the sanitary sewer system in your area until it reaches a wastewater treatment facility or a septic system.

4. Fill Valve Refills the Bowl and Tank

Once you let go of the flush handle and the toilet tank drains, the flush valve should fall back into place and allow the tank to refill. Water from your home's supply lines enters the toilet tank through the refill valve, which simultaneously fills the toilet bowl and tank.

5. Float Ball Regulates Water Levels 

Every toilet tank has a floating device inside it called a float ball. As the water level in your toilet tank rises, this float ball rises at the same time. At a certain point, the float ball rises high enough to cut the valve off. If this float ball becomes detached, it will cause your toilet tank to overflow.

How an Automatic Toilet and Urinal Flush Sensors Work

An automatic toilet flush is hygienic and convenient (albeit startling at times). There isn’t a ghost by the toilet; instead, the device uses infrared beams to detect whenever a user is near. Here’s a breakdown of how a toilet flushes when it’s automatic.

1. Infrared Sensor Detects Movement

An automatic toilet flusher works with a sensor containing two infrared LEDs. One emits infrared beams while the other receives them. Once the user gets close enough to the toilet, it reflects the infrared light to the receiver.

2. Solenoid Valve Opens the Water Flow

Once the infrared sensor detects movement, it sends a signal to the solenoid valve. This valve will then open up the water flow, sending wastewater out.

3. Power Source Keeps the Toilet Working

Unlike traditional toilets that rely on manual activation and gravity to flush the toilet, an automatic-flush toilet requires power to operate. The three basic types are DC battery, AC power supply, or combined AC/DC. The whole operation gets controlled via a microchip that flushes on a timer.

How a Dual-Flushing Toilet Works

Dual-flush toilets conserve water by having different flush options for solid and liquid waste. Liquids get a half-flush that uses less water. However, the function is a bit differently than a regular toilet flush. Let’s have a look at what happens.

1. Each Button Activates a Large Trapway 

Rather than a regular toilet siphoning action, a dual-flushing toilet employs a large trapway, which is the hole at the bottom of the toilet.

2. Wastewater Exits the Toilet Bowl

Depending on which button gets pressed, the trapway pushes the proper amount down the drain. As mentioned, this is either a half-flush that uses far less water or a full flush. The full flush still uses less water than traditional toilets due to the efficiency of the trapway.

Parts of a Toilet

There are two main parts to your toilet: the tank and the bowl. Understanding these parts (and the components within them) will help you diagnose and treat an issue if it occurs.

Toilet Tank

The toilet tank is the large, rectangular area on top of the bowl. It holds approximately two gallons of reserve water that’s released upon flushing. Housed within the tank are many of the key components of a toilet system:

• Handle: Long arm extending into the toilet tank, attached to a chain. When flushed, this arm pulls the chain and releases the flapper. 

• Chain: Usually metal, the toilet chain connects the handle to the toilet flapper. When the handle is flushed, the chain lifts up, lifting the flapper. 

• Flapper: This part seals the opening between the tank and the toilet bowl. If your toilet continues to run, it may be time to switch out your flapper.

• Fill valve: After the water is removed from the tank, the fill valve refills the water tank using the toilet float as a guide.

• Toilet float: This is a buoyant ball (usually rubber or aluminum) that regulates the amount of water in the tank.

Toilet Bowl

The toilet bowl is what you sit on when you use the restroom. When the water empties from the toilet tank above, it rushes into the toilet bowl and is siphoned away via gravity into the sewage system. 

• Rim holes: Small holes along the seat’s rim that allows water to rush in. This water is meant to rinse the sidewalls of the bowl, not necessarily flush the water.

• Siphon jet: This part is the bigger water jet or vacuum valve that flushes water through the bowl and out the trapway. You can tell the siphon jet is clogged if the water isn’t swirling around the bowl and is instead coming straight down.

• Trapway: This is the opening at the bottom of the toilet that water travels through to get out. 

• Outlet: The base of your toilet bowl connecting to all floor plumbing. It’s sealed with a wax seal and toilet flange. 

• Wax seal: The toilet bowl seal secures the base of the toilet to the toilet flange. If water is leaking from the base of the toilet, your wax seal may be broken.

• Toilet flange:  Sealed with the wax ring, the toilet flange mounts the toilet onto the floor and connects it to the drain.

• Lid and seat: The top portion of the toilet bowl that makes it more comfortable to use.

Navigating Common Toilet Troubles

Unfortunately, toilets can malfunction from time to time. Luckily, many common problems are resolved with simple DIY toilet fixes. You might also hear a noise in the wall when the toilet flushes, which could indicate a few different issues. 

Depending on what has gone wrong, you may need to replace the toilet, get it repaired, or execute some troubleshooting. There are some helpful how-to's online, but get in touch with a top-rated local plumber if you're in over your head.