How a Gravity-Flush Toilet Works

In today’s technology-driven world, it’s impressive that a piece of equipment we use every day hasn’t changed that much in over 400 years. We’re talking about the gravity-flush toilet. If you’ve always wondered how exactly the toilet works but were too afraid to ask, today is your lucky day.

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What does gravity-flush mean?

For the majority of toilets found in homes, when you flush, the only thing that is forcing water and its contents down the drain is gravity. That means no extra pressure, electrical, or mechanical force is needed. This also means that the design of the toilet is fairly simple because it has few moving parts that can break.

What happens when you flush the toilet

Before it’s time to flush the toilet, a water supply line fills the tank with water (this is the only part of the process with pressurized force). When you push the handle to flush, a lever inside the tank lifts a chain that pulls the flapper valve up. This action uncovers the hole in the tank, also known as the flush valve opening. This is when gravity jumps into action, pushing water in the tank down through the flush valve opening down into the bowl.

The water is then directed through a few holes along the rim of the toilet bowl. This flow of water creates a circular pattern, which helps push the contents of the bowl down the drain. The force of the gravity should be strong enough to move everything through the trap, which is a bend in the channel in the base of the toilet before it drains into the sewer drain in the floor.

Back up to the tank. After the flush cycle, the water supply line turns back to refill the tank and bowl. A float ball or cup raises along with the water and turns off the fill valve when the water reaches a certain level.

Common issues with a gravity-flush toilet

The design of the toilet is very effective – but nothing is ever perfect. There are a few common issues that you can look out for.

  • The lift chain can get tangled or break, preventing the toilet from flushing
  • The rubber of the flapper can wear out, breaking the seal to the flush valve and causing the toilet to run constantly
  • The refill tube can fall off, preventing water from refilling the bowl and tank
  • The fill valve is not adjusted properly, leading to water to rise too high or too low for proper flushing

Thankfully because of the simple design, the toilet is usually easy and inexpensive to fix. See, we told you this was a pretty impressive fixture.

Plumbers in Oahu and Maui

At Emergency Plumbing & Solar, we want everyone to be comfortable and safe in their homes. Whether you need help with a single clogged drain or a complete home remodel, we’re happy to lend our expertise. Give us a call today at (808) 691-9309.


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