Council inspections indicate gully traps often too low

12/12/2014 12:00 a.m.

Five weeks into its new Right Pipe project, Ashburton District Council is discovering that a number of properties' gully traps are lower than what is legally required under current legislation.

Launched in the first week of November, the Right Pipe project involves inspecting the drainage systems of all residential properties in the urban Ashburton area to ensure stormwater runoff is draining into the correct pipe network. 

By carrying out this work, Council will be able to identify where incorrectly constructed drainage systems are resulting in stormwater entering the Council's sewerage network.

Council's Asset Manager Andrew Guthrie says of the 100 Tinwald properties inspected to date, almost half of the gully traps have been below the levels the New Zealand Building Act requires.

"The issue with gully traps being too low is that when excessive rain events occur, stormwater goes into the wrong drainage system – the wastewater system – but gully traps are not intended to receive stormwater," he says.

"To help make sure your drainage system is up to date before we do an inspection, we recommend you check the height of your gully traps and if they're not the minimum required (100mm above unpaved areas, & 25mm above paved areas) get them raised".

"It is vital that we keep stormwater and sewerage networks functioning as two separate systems."

The Right Pipe project will be carried out over the next one to two years as the Council works through each area, property-by-property. 

"While we are confident that remedial work on incorrectly constructed drainage systems will result in improvements over time, we have to keep in mind that there is no guarantee stormwater won't still enter the sewerage network, especially during heavy rain events," he says.

The Council's ongoing sewerage network assessment will continue, with a focus on identifying those pipes in the poorest condition that allow groundwater to enter the network and replacing those pipes through the renewal programme.

"Taking this two-pronged approach to the issue will give us the best result in terms of reducing water entering the sewerage network during rain events," says Mr Guthrie.

Prior to inspection, Council will notify property owners of the scheduled date and time of the inspection. 

Following an inspection, Council will advise the property owner of the results, including whether their drainage system meets the required standards and what work, if any, is needed to get it up to standard. 

For information about the Right Pipe project, property owners can call the Council Customer Services Team on 307 7700 or:

Click here to find out more about the Right Pipe Project


Page reviewed: 24 Dec 2014 11:38am