4 Key Features of a Siphonic System for Better Drainage

Key Features of a Siphonic System
FacebookTwitterGoogle PlusLinkedIn

If you are not familiar with rain drainage systems, you may not be aware of how important they can be.

According to the Australian Bureau of Meteorology, in Australia last year, the average rainfall was around 502 millimetres, making it the 30th wettest year on record. Looking at these statistics, the trend over the next few years implies that it is most likely going to rise.

If you want to get the most out of your rainwater, you need to install a reliable and efficient siphonic system. Read on to discover some of the features that make it the best rainwater drainage system on the market.

What is a Siphonic System?

First, let us handle the basics.

In contrast to typical roof drainage, a siphonic drainage system uses the 100% fill ratio of the pipe. It is designed to siphon water down the inlet at a high velocity and in such a way that no air comes in.

There are four main elements to this drainage system that make it so efficient. These include the double intake lip, the air baffle, stainless body outlet, the pipework and a cleverly engineered design.

Double Intake Lip

Large debris can be a major issue for drainage pipes. The purpose of a double intake lip in a siphonic system is to provide another drainage route for this debris if it enters the gutter and attempts to surround the outlet.

It has a shape that works in such a way that water can flow in easily, but twigs, leaves, and other debris cannot.

Air Baffle

The unique feature of the siphonic drainage system is the air baffle. The primary purpose of the air baffle is to stop air from entering the pipe system and to create a high-velocity siphonic flow.

A regular draining system pulls not only water but also air into its pipes through a hole set into a low point on the roof. Not only does this diminish the capacity of the pipes, it slows down the flow of water and makes the piping inefficient.

According to drainage experts, with a conventional drainage system, only around 20 to 33 percent of the drain gets filled with water while in use. This leaves anywhere between 70 to 80 percent of the pipe's capacity lost to the air.

In contrast to this, siphonic drainage systems have little to no air within them, and this is thanks to the air baffle and anti-vortex fins. If air isn't present, it can't go into the pipe and form into a vortex during heavy rainfall.

This means that the water will only get pulled down by gravity in an almost vacuum sealed state. This allows the water to fill the pipes at 100 percent capacity, resulting in high-velocity water drainage running at self-cleansing velocities.


Compared to a conventional drainage system, a siphonic drainage system has less pipework. Not only does this make it more environmentally friendly than a regular system, but also it makes water flow more efficiently into a stormwater system or collection tank.

These systems also don't need huge thick pipes in order to drain stormwater. In the past, bigger pipes were needed in order to maximise flow for a conventional system. With the use of a siphonic based system, however, large pipes are not as necessary.

Since water will flow at a maximum velocity within a siphonic system, you can use smaller pipes instead, thus saving money and space. Each outlet doesn't need to run all the way into the ground level independently. Instead, several outlet drains can all be attached to a single collector pipe, like a manifold.

This collector pipe can then be routed to one downpipe. This entire process increases the velocity of water drainage and helps to transport water out of the building.

These pipes are available in a range of types, typically HDPE but FRC and stainless steel are available as well.

Steel Outlet Body

One very important aspect of the siphonic drainage system that is often overlooked is the steel outlet body that attaches the drain to the pipe. If this is not of the highest-quality, it can severely affect the flow of the water into the pipes.

A low-quality outlet body corrodes over time. The corrosion creates holes where the water can leak out from thus reducing the efficiency of the drainage system entirely. In many siphonic drainage systems, this outlet body is made from materials like stainless steel.

Stainless steel provides excellent corrosion resistance and will allow water to be sucked through without the chance of long term corrosion.

Benefits of a Siphonic System

As you can see, siphonic drainage systems have a variety of features that make it beneficial to any building drainage system. However, there are even more benefits to a system such as this one!

1. Horizontal Routing

With its unique water draining method, this type of system can be routed horizontally throughout a building. This means you don't need to fit pipes onto a gradient.

2. Fewer Downpipes Required

Unlike a conventional draining system which relies on large amounts of downpipes, this system is much more space efficient. In fact, siphonic draining systems require up to 80% fewer downpipes.

This results in cost savings for anyone installing the system and a reduction in associated groundwork. Not only this, but there is much more lettable area for commercial and retail buildings.

3. Freedom of Design

Due to the way, it's designed, siphonic draining systems give the builder or engineer complete control over the discharge location of the downpipe. This means there is plenty of design flexibility.

Furthermore, the rainwater collected by these pipes can be manipulated into collection tanks for rainwater harvesting. Specialist filters can be used to further increase the water quality in a rainwater tank.

4. Easy Construction

As there are fewer pipes to install and system parts to connect, a siphonic based drainage system is a lot quicker to set up. This reduced construction period will save you time and money as well as providing flexible construction sequencing.

5. Self-Cleaning System

A big problem that a lot of conventional drainage systems face is getting clogged with debris and sediment. This is due to a lack of consistent water flow that is not at a high enough velocity to clear blockages.

Siphonic systems, however, are self-cleaning due to the high-pressure and high flow rates. This minimises maintenance costs.

Closing: Install Your Siphonic System Before the Rains Come!

With a team of siphonic system experts to assist you, you can expect a high-quality, high-velocity drainage system that will last in the elements for years to come making sure you sleep well on a rainy night.

For more information, contact us here.

If you want to find out more