Two networks, two different purposes.
The sewer and stormwater networks are separate systems.
- The stormwater network protects against flooding. Stormwater pipes collect rainwater run-off and direct it into the stormwater network where it is fed into the waterways.
- The sewer network protects health and the environment. The sewerage network carries sewage from bathrooms, kitchens and laundries to treatment plants for processing.
Property owners need to ensure stormwater does not enter the sewer sytem around their home. Excess water in the sewer may cause pipes to become overloaded and lead to sewage overflows in people's properties. To protect your home, check that water from your roof downpipes, pool backwash and landscaping run-off is not diverted into the sewerage system.
For more information read the Keep stormwater out of the sewer brochure.
Who is responsible for maintaining the sewerage system?
Your responsibilities as the property owner
Property owners are responsible for the installation, repair, maintenance and replacement of all the private fittings and pipes on their property up to the sewer connection point. If a leak or blockage is detected in these pipes, it is your responsibility to fix it. We recommend you contact a licensed plumber to rectify the problem as soon as possible.
We are responsible for the maintenance and repair of the pipes leading away from the connection point to the street. If a problem is detected in these pipes, it is our responsibility to fix it. To report a fault, please contact us on 1800 245 092 or visit the Report a fault or damage page.
How to prevent blockages?
Blockages occur when there is something inside your pipe that stops it working properly. About 20% of all blockages in our sewerage system result from putting the wrong things down sinks and toilets. You can find out more on the fact sheet Think before you put it down the drain.
You can protect your home from sewer blockages and keep your drains flowing by following these simple tips:
Garden and driveway
- Do no pour used motor oils or other hazardous chemicals down the drain. Contact your council for information on safe disposal.
- Nappies, sanitary products and other personal hygiene items belong in the bin.
- You can also place a strainer on your shower drain to catch loose items.
- Don't use the sink as a garbage bin for food scraps. Coffee grinds and tea leaves should also be disposed of in the bin.
- Use a sink strainer to catch small items and scraps before they get washed away.
- Don't pour boiling water down the sink. Water in excess of 65 degrees celsius could damage PVC pipes.
- Cooking oils and fats often harden in drains creating greasy plugs which can clog your pipes.
- Use the recommended dose of detergent to avoid build-up in your washing machine and laundry pipes.
- Biodegradable and phosphate-free products are also kinder to the environment and less likely to cause blockages.
For the medical term, see Drainage (medical).
See also: Storm drain and Stormwater
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area. The internal drainage of most agriculturalsoils is good enough to prevent severe waterlogging (anaerobic conditions that harm root growth), but many soils need artificial drainage to improve production or to manage water supplies.
The ancient Indus of sewerage and drainage that were developed and used in cities throughout the civilization were far more advanced than any found in contemporary urban cities in the Middle East and even more efficient than those in some areas of the Indian Subcontinent today. All houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered gravity sewers, which lined the major streets.
18th and 19th century
The invention of hollow-pipe drainage is credited to Sir Hugh Dalrymple, who died in 1753.
New drainage systems incorporate geotextile filters, including Woven and Non-Woven Geotextiles, that retain and prevent fine grains of soil from passing into and clogging the drain. Geotextiles are synthetic textile fabrics specially manufactured for civil and environmental engineering applications. Geotextiles are designed to retain fine soil particles while allowing water to pass through. In a typical drainage system they would be laid along a trench which would then be filled with coarse granular material: gravel, sea shells, stone or rock. The geotextile is then folded over the top of the stone and the trench is then covered by soil. Groundwater seeps through the geotextile and flows through the stone to an outfell. In high groundwater conditions a perforated plastic (PVC or PE) pipe is laid along the base of the drain to increase the volume of water transported in the drain.
Alternatively, a prefabricated plastic drainage system made of HDPE called SmartDitch, often incorporating geotextile, coco fiber or ragfilters can be considered. The use of these materials has become increasingly more common due to their ease of use which eliminates the need for transporting and laying stone drainage aggregate which is invariably more expensive than a synthetic drain and concrete liners.
Over the past 30 years geotextile and PVC filters have become the most commonly used soil filter media. They are cheap to produce and easy to lay, with factory controlled properties that ensure long term filtration performance even in fine silty soil conditions.
21st century alternatives
Seattle's Public Utilities created a pilot program called Street Edge Alternatives (SEA Streets) Project. The project focuses on designing a system "to provide drainage that more closely mimics the natural landscape prior to development than traditional piped systems". The streets are characterized by ditches along the side of the roadway, with plantings designed throughout the area. An emphasis on non curbed sidewalks allows water to flow more freely into the areas of permeable surface on the side of the streets. Because of the plantings the run off water from the urban area does not all directly go into the ground but can also be absorbed into the surrounding environment. According to the monitoring by Seattle Public Utilities, they report a 99 percent reduction of storm water leaving the drainage project
Drainage has undergone a large-scale environmental review in the recent past in the United Kingdom. Sustainable Urban Drainage Systems (SUDS) are designed to encourage contractors to install drainage system that more closely mimic the natural flow of water in nature. Since 2010 local and neighbourhood planning in the UK is required by law to factor SUDS into any development projects that they are responsible for.
Slot drainage has proved the most breakthrough product of the last twenty years as a drainage option. As a channel drainage system it is designed to eliminate the need for further pipework systems to be installed in parallel to the drainage, reducing the environmental impact of production as well as improving water collection. Both stainless steel and concrete channel slot drainage have become industry standards on construction projects.
Drainage in the construction industry
The civil engineer is responsible for drainage in construction projects. They set out from the plans all the roads, street gutters, drainage, culverts and sewers involved in construction operations. During the construction process he/she will set out all the necessary levels for each of the previously mentioned factors.
Civil engineers and construction managers work alongside architects and supervisors, planners, quantity surveyors, the general workforce, as well as subcontractors. Typically, most jurisdictions have some body of drainage law to govern to what degree a landowner can alter the drainage from his parcel.
Drainage options for the construction industry include:
- Point drainage, which intercepts water at gullies (points). Gullies connect to drainage pipes beneath the ground surface and deep excavation is required to facilitate this system. Support for deep trenches is required in the shape of planking, strutting or shoring.
- Channel drainage, which intercepts water along the entire run of the channel. Channel drainage is typically manufactured from concrete, steel, polymer or composites. The interception rate of channel drainage is greater than point drainage and the excavation required is usually much less deep.
The surface opening of channel drainage usually comes in the form of gratings (polymer, plastic, steel or iron) or a single slot (slot drain) that runs along the ground surface (typically manufactured from steel or iron).
Drainage in urban vegetation
Research evaluating drainage quantity and quality in urban mixed landscapes vegetation is limited. Insufficiencies and obstacles in understanding soil water conditions particularly in urban landscape environs undermine a sound judgement of urban soils. A research in South Australia investigates the relative impact of landscape variation on drainage and solute leaching in a public park containing heterogeneous urban-landscape vegetation that is irrigated with recycled wastewater. For this purpose, two pan lysimeters were designed and installed in two different land-scape zones.
Reasons for artificial drainage
Wetland soils may need drainage to be used for agriculture. In the northern United States and Europe, glaciation created numerous small lakes which gradually filled with humus to make marshes. Some of these were drained using open ditches and trenches to make mucklands, which are primarily used for high value crops such as vegetables.
The largest project of this type in the world has been in process for centuries in the Netherlands. The area between Amsterdam, Haarlem and Leiden was, in prehistoric times swampland and small lakes. Turf cutting (Peatmining), subsidence and shoreline erosion gradually caused the formation of one large lake, the Haarlemmermeer, or lake of Haarlem. The invention of wind-powered pumping engines in the 15th century permitted drainage of some of the marginal land, but the final drainage of the lake had to await the design of large, steam powered pumps and agreements between regional authorities. The elimination of the lake occurred between 1849 and 1852, creating thousands of km² of new land.
Coastal plains and river deltas may have seasonally or permanently high water tables and must have drainage improvements if they are to be used for agriculture. An example is the flatwoods citrus-growing region of Florida. After periods of high rainfall, drainage pumps are employed to prevent damage to the citrus groves from overly wet soils. Rice production requires complete control of water, as fields need to be flooded or drained at different stages of the crop cycle. The Netherlands has also led the way in this type of drainage, not only to drain lowland along the shore, but actually pushing back the sea until the original nation has been greatly enlarged.
In moist climates, soils may be adequate for cropping with the exception that they become waterlogged for brief periods each year, from snow melt or from heavy rains. Soils that are predominantly clay will pass water very slowly downward, meanwhile plant roots suffocate because the excessive water around the roots eliminates air movement through the soil.
Other soils may have an impervious layer of mineralized soil, called a hardpan or relatively impervious rock layers may underlie shallow soils. Drainage is especially important in tree fruit production. Soils that are otherwise excellent may be waterlogged for a week of the year, which is sufficient to kill fruit trees and cost the productivity of the land until replacements can be established. In each of these cases appropriate drainage carries off temporary flushes of water to prevent damage to annual or perennial crops.
Drier areas are often farmed by irrigation, and one would not consider drainage necessary. However, irrigation water always contains minerals and salts, which can be concentrated to toxic levels by evapotranspiration. Irrigated land may need periodic flushes with excessive irrigation water and drainage to control soil salinity.
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