How It Works: Dual Flush Syphon

Here at Viva, a common question we get asked is how does a dual flush syphon actually work and how does holding the handle down create a half flush?

How does a syphon work?
The syphon is a type of flush valve which acts as an internal plunger. When the handle is pressed, the syphon draws up the water which then passes through a folding diaphragm washer before bridging over to the syphon outlet. At this point gravity takes over and continues to draw out the remaining water until the cistern is completely empty.

So how do I get a half flush by holding the handle down?

Straw In Glass
Imagine drinking a glass of water through a straw with a hole in it. The straw would actually be fully functional until the water level dropped below the hole. At this point you would be drawing air instead of the water. This is similar to how a syphon works.

A half flush is created by breaking the water suction midway through the flush. With a Skylo syphon this is achieved when the toilet handle is held down. How? …the secret is in the stem! Cuts In Syphon Stem
A Skylo syphon has four extruded cuts around the bottom section of its stem. This allows air to enter the syphon which breaks the air tight seal at the midway point of a flush. This results in 50% of the water remaining in the cistern.

Here is a cool video animation showing you how it works:

Want to know more about the benefits dual flush and saving water check out our article What is Dual Flush.

Now you know, give them a try for yourself.

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