How Does a Toilet Work?

The toilet is probably the least glamorous device in our homes but one of the most essential. We both rely on it and try to never think about it. As much as we don’t want to think about toilets, we cannot dispute the fact that they are important and their use has greatly increased humankind’s hygiene and quality of life.

So, how exactly do toilets work? All flush toilets, from Edmonton to Timbuktu, use the same principle. That principle is gravity. The toilet tank (also called the cistern) empties into the toilet bowl using gravity, emptying and cleaning the bowl for future use. The tank just needs to be large enough to hold enough water to produce the force needed to properly clean the bowl.

Truthfully, it’s a little more involved than just water emptying into the toilet bowl. There are several components working together to make sure your toilet flushes.

The water in your toilet tank is filled through a supply line coming from your plumbing system and entering the bottom or side of the tank. The water is directed by the ballcock into the tank and toilet bowl. The toilet stops filling the tank once the float ball reaches a certain point and puts pressure on the ballcock which then turns off the flow of water.

When you flush your toilet, the handle lifts a lift rod or chain which raises the flapper (it covers the hole at the base of the tank called the flush valve seat). Gravity then pulls the water into the bowl through small passages under the toilet’s rim. The water then rushes into the bowl creating a cyclone effect — like a mini tornado — carrying the waste down and out through the drain.

Pretty much immediately the flapper drops back into position, covering the flush valve seat, and the tank starts filling again.

An integral part of your toilet is the S-trap (also called the S-bend), which is the big s-shaped pipe at the base of the toilet. Some water is always in this pipe and seals off the sewage pipe the waste enters. This little bit of water has a very important job. It stops germs and bad smells from exiting the sewage pipe and entering your bathroom. When the exiting water goes through the S-trap it produces a siphon, sucking the water down the pipe and properly emptying the bowl.

The toilet, the loo, the throne, whatever you want to call it, is a critical device in our daily lives. Like so many things, the concept is simple but in practice it’s a bit more involved. We hope our explanation has satisfied your curiosity on how they work.