Toilet Advice

How Toilets Work

We've all got a toilet in our bathroom. But have you ever wondered how it works? We look at the various parts and mechanisms below to help you understand how they are able to flush out waste.


A toilet is made up of many different parts. The seat, tank, bowl, water supply line, flapper, refill tube, float, and floor flange among them.

There are three different systems that bring all these things together. The first is the flush mechanism, the second is the siphonic bowl, and the third is the refill system. Lets take a closer look at what each of these things do.

Siphonic bowl

A siphonic bowl usually include a S shape or reverse P shape trap passageway. One side of the trap will be where water enters the bowl and creates the water spot, the other will lead to the waste outlet and drains.

Imagine you don't have the tank installed, leaving just the bowl in place. You can conduct an experiment by pouring small amounts of water into the bowl. You may notice not a lot changes in terms of water level. The reason for this is that the water level on the other side of the trap curve rises above the siphonic tube and goes down the waste pipe.

However, if you perform the same experiment, with a much larger volume of water (2 gallons would suffice), you'll see that it begins to act the same way as it would if you pulled the trip lever. Why is this? If you send enough water through the bowl fast enough, it will fill the siphon tube, displacing the air creating a vacuum which sucks the rest of the water out and through the waste outlet.

If you're ever in a situation where your tanks flush mechanism isn't working, you'll still be able to flush the toilet. Just fill up a bucket of water and pour it in. This can be used as a temporary fix until you get a plumber round.

Flushing mechanism

The tank stores the water required to perform the same task as our bucket did in the experiment above. The quantity of water varies, but most products use either 1.6 gallons or a more efficient 1.28 gallons per flush.

To activate the siphonic action, water has to enter the bowl quite fast. It does this by releasing the water through a flush valve (that pulling the trip lever lifts), typically measuring 2 or 3 inches. This is big enough to clean the bowl of waste.


After you've released the water contents of the tank, you let go of the lever or button, which shuts the flush valve. The refill mechanism then begins to fill the tank up again ready for the next flush. It does this by using another valve which is operated via a ball float that rises or falls with the water level in the tank. Once it gets to a certain level, this valve closes not letting any more water into the tank.