Inflow and Infiltration

Property Inspections

The Clutha District Council is undertaking a district-wide property inspection programme to identify any issues with inflow and infiltration (I&I) to our sewer collection system.

Council employees will be going door-to-door undertaking visual checks of stormwater and sewerage utilities at your property.

When property inspections are being undertaken in your area the Clutha District Council Water Technician will be wearing an orange vest and carrying a warrant card so he will be easily identified. If you have any queries regarding our Water Technician entering your property, please phone Clutha District Council on 03 419 0200 or 0800 801 350.

If you have any other enquiries regarding I&I and to update Council with the outcome of I&I property inspections please email inflowenquiries@cluthadc.govt.nz with the effected property's address and contact details)

What is Inflow and Infiltration?

Inflow and Infiltration refers to rainwater and groundwater that enters the wastewater system through a variety of defects on public and private property.

Inflow is the direct discharge of stormwater (i.e., rainwater) entering the sewer collection system, often from low lying gully traps, yard drains, roof downpipes and cross connections from stormwater drains that connect directly to the sewer.

Infiltration is the stormwater that seeps into the ground and enters the sewerage system, including sewer service connections, through defects, cracks, and joints in the pipe.

A gully trap collects wastewater from the kitchen, bathroom and laundry. Gully traps that are not set up correctly can allow stormwater runoff to enter them and into the wastewater system where it shouldn’t be. Gully traps must be installed no less than 25mm above a paved surface such as a concrete driveway or foot path and no less than 100mm above an unpaved surface such as gardens and grass areas.

Sources of Inflow and Infiltration

Next steps, how can you help?

Once the inspection has been completed, property owners will be contacted regarding the findings and advice on remedial actions. As a property owner, you play an important role in addressing this issue and helping to reduce the risk of overflows. If you find any issues that you can easily resolve, we encourage you to do this.

Legal requirements

Clutha District Council Water Services Bylaw 2019
New Zealand Building Code G13 – Foul Water

31(1a) and 32(3), of the Clutha District Council Water Services Bylaw 2019:

“No person may cause or allow Stormwater to enter the Sewerage System unless specific approval is given.”

Why are we doing this?

When heavy rain hits the Clutha District wastewater can get into our waterways and has a detrimental effect on our environment.

During heavy rain, increased inflow and infiltration can overwhelm our sewer system, it can increase up to 10 times more than the average daily flow, which then causes overflows.

This increases the cost associated with wastewater pumping and treatment and can lead to the contamination of private properties and the environment.

This is not a new issue and it is not just happening in Clutha, but it is something that Council must address as what was accepted in the past is no longer allowed.

Council has started various initiatives to reduce the inflow and infiltration to our sewer collection system. These include:

Private property inspections
Sewer Manhole inspections
CCTV inspections of the sewer mains
Sewer renewals.

Inflow and infiltration Inspection Programme

Location	Planned Inspection Dates
Owaka	December 2024
Heriot	January 2025
Milton	February - April 2025
Lawrence	May - June 2025
Kaitangata	July – August 2025
Waihola	September 2025
Clinton	October 2025
Stirling	November 2025

Like more information?

More information about Council-operated water supplies can be found from:

Council’s latest Long Term Plan (available on the website and at Council’s Service Centres)

Contact Council’s Service Delivery Department on 0800 801 350

Report a Problem

Like any service, Council’s water supply can occasionally have a problem. It might be discoloured water, or the sudden appearance of a leak in a pipeline, or something else. If you discover a problem download Council’s Antenno app and report it or call us so that we can investigate, repair the problem, and get the service back to normal.

Report a Service request or stormwater problem Call 03 419 0200 or 0800 801 350 (Toll Free in NZ)

After Hours or Emergency call 0800 801 350

Email help.desk@cluthadc.govt.nz

Inflow and Infiltration Inspections Brochure

If you want a copy of this information feel free to print this page or download our Inflow and Infiltration Inspections brochure: