MEDIA RELEASE

Infiltration and Inflow Testing To Begin

ManukauCity (18 March 2008) – A programme to make sure rain and stormwater is not entering the wastewater (sewerage) system will begin in Manukau over the next month.

Manukau Water Limited will be carrying out tests to locate possible faults in both public and private drainage which might be allowing stormwater into the wastewater system. The testing includes inspection of private drainage; such as gully traps, down pipes and manholes; and smoke testing of sewer pipes.

In periods of heavy rain, a sudden increase of water flowing into the sewerage system can result in overflows, which can lead to contamination of private properties and watercourses. The excessive flows can also lead to reduced levels of treatment at wastewater treatment plants due to system overloading.

Manukau Water Limited aims to inform its customers of the possibility of rainwater inflow and infiltration into the system, and to help prevent this by inspecting properties that might be at risk. Where a fault is detected it will need to be corrected. This might require the services of a builder, plumber or drainlayer.

The company will shortly begin a testing programme in the SpinnakerBay area of Manukau. It will carry out a number of tests including inspecting private drainage such as gully traps, down pipes and manholes. Manukau Water Limited will also undertake smoke testing of wastewater pipes, using a small machine to blow smoke into sewer pipes. This smoke is white, cold, non-toxic, non-irritating and completely harmless. It allows inspectors to see if stormwater can enter the wastewater system. If the system is working properly, the smoke will be released from ventilation points in the system but if the smoke discharges from downpipes or other points it will identify a problem that requires further investigation.

The testing will require access onto some private properties but Manukau Water Limited team members will not enter houses. All of the company’s team members carry identification cards.

Property owners will be advised by letter prior to the testing actually taking place on their property.

Manukau Water Limited encourages all property owners to ensure appropriate devices are installed to prevent inflow and infiltration into the sewerage system.

Infiltration and Inflow
Manukau Water Limited is committed to providing safe, high quality water and wastewater services to our customers at all times. As part of this service commitment, we want to ensure that conditions known as “infiltration” and “inflow” do not occur in your wastewater system.

What are infiltration and inflow?
Infiltration and inflow are problems that can seriously affect the effectiveness of the sanitary sewer systems that treat waste water from the community. Sanitary sewers collect waste flows from inside houses, offices, schools and other buildings. Wastes from sinks, basins, baths and showers flow through this network to the Wastewater Treatment Plant, where they are extensively treated.
Meanwhile, rainfall on roofs, roads, yards and driveways should run off through stormwater grates in road gutters, yards and parking lots into stormwater pipes. These pipes then carry this runoff to streams and ultimately to the sea.
Infiltration and inflow are the technical terms that refer to when rain and stormwater enters the sewerage system.
Infiltrationrefers to rainwater and ground water that seeps into the system through defective pipes and joints.
Inflowrefers to stormwater and surface water that enters the sewer directly. This is usually from local flooding into low-lying gully traps, and roof downpipes being directly connected to the sewer.
In periods of heavy rain, the sudden increase in Inflow to the Sewerage Network can result in overflows, which can lead to contamination of private properties and watercourses, or it can lead to reduced levels of treatment at the Wastewater Treatment Plant due to system overloading.

What is Manukau Water Limited doing about Inflow and Infiltration?
We are promoting an inflow and infiltration programme throughout Manukau City. Our aim is to inform all of our customers of the possibility of inflow and infiltration, and to help prevent this by inspecting properties that may be at risk and ensuring that those properties which are at risk have taken measures to prevent these problems occurring.

How can Inflow and Infiltration be detected?
There are a number of tests that can be carried out to locate faults in drainage which might be allowing stormwater into the public wastewater system. Inspection of private drainage, ie gully traps, down pipes, manholes can be carried out while coloured smoke can be used to test for leaks in sanitary sewer pipes.

What are the legal requirements for preventing inflow and infiltration
Manukau Water Limited is required to ensure appropriate devices are installed and maintained to prevent inflow and infiltration into the sewerage system. Buildings and houses must comply with the requirements of the Building Regulations, 1992 and the Building Act 1992 to prevent inflow and infiltration.
Note: There are other acts and regulations that may impact on the requirements for inflow and infiltration prevention and control of cross-connections
How can I prevent inflow or infiltration?
If a fault is detected on your property you will need to have it corrected. This might require the services of a builder, plumber or drainlayer.

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