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Drainage systems: Why we have them and how they work

In countries and cities around the world that function without adequate and effective drainage systems, sewage will more often than not contaminate water supplies that are used for drinking and bathing. This exposes the people living in the area to diseases, such as cholera, typhoid, dysentery and many more awful illnesses and conditions.

Consequently, drains and sewers that operate and function properly are clearly very import – but how do they actually work?

Drainage systems

The most crucial elements of functioning and operational drainage systems are the vents, the traps and, of course, the pipes.


In modern plumbing, a drain-waste-vent is a crucial component to drainage systems as it allows air to enter a sewerage system to maintain proper air pressure. This enables the removal of sewage – waste that is produced from applications such as toilets, sinks and showers – from a dwelling.

Without the air supply coming from the vents, the wastewater that runs down the piping network would not flow out properly. Proper venting is required to avoid a vacuum effect from being created.


Traps are important as they are designed to prevent any sewage from entering the building the drainage system it is a part of. The component is designed to trap liquid and gas – most notably sewer gases – while at the same time allowing waste materials to pass through.

The trap is the curved or S-shaped section of the pipe connected to the drain. Water flows through the trap and out through the drainpipe with enough water being caught to form a seal and stop unwanted sewer gas from flowing up.

Sewerage pipes

Raw sewage will be carried from homes and buildings via the drainage systems into an extensive and underground sewerage system. Sewerage pipes are always laid on a slope, this allows sewage to properly flow to its nearest pumping station. From there it will be directed to a treatment facility.

These large networks of sewerage system pipes are quite capable of handling normal sewage, however there are certain substances and situations that can cause blockages and overflows. For example, large amounts of storm-water can cause a sudden overflow and the illegal discharge of trade waste can cause operational problems, which require careful and expert management.

AWD Civil are the experts in managing and planning diverse sewage infrastructure and intricate drainage systems. If you have a project that needs doing contact our team at 07 3200 5766.

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