Downloads & FAQs

What is the main source of Inflow and infiltration?

Each sewerage network is different however sewer manholes generate a disproportionate amount of I/I. Assessing and identifying major contributors is an important tool to help water authorities take action to mitigate problems.

What is the most common cause of I/I?

While there are a number of causes of I/I, typically the most common is failed joints in both new and old assets. This can be in maintenance holes (particularly the chimney or neck where there are often multiple joints close together and near the surface) as well as pump stations, pits and pipes

What are the environmental benefits of controlling I/I ?

Minimizing wasted electricity required to pump and treat water that has entered the sewer; reduced chemical consumption in treatment plants; reduced risk of sewage contaminating the environment.

How can I quickly check to see if I/I is occurring in my network & where should I start?

The simplest approach is to look at how sewage flow changes during and immediately after rain events. If sewage flow increases (either at the treatment plant or at pump stations) then rainwater and / or ground water is entering the network.

If sewage flow increases but we don’t get many overflows, does I/I really matter?

Any additional water that is allowed to leak into the sewerage network increases the operational costs, the wear and tear on sewerage assets through increased power consumption, erosion and siltation and risks environmental impacts in the event of an overflow. It may also result in excessive capital and unnecessary over design of infrastructure to accommodate I/I, all of which needs to be paid for and typically, this ends up as a higher user charge.

We do not have experience or equipment to investigate I/I what can we do ?

There are options for councils and water authorities to get specialist contractors to do preliminary investigations through to detailed studies. Working with specialists and contractors experienced in I/I will allow you to determine what your I/I assessment and management goals are and tailor a staged plan and program to suit your specific circumstances and budget. If you need help with this, get in touch with us and we'll help.

Do we need to do Flow gauging, 3D scanning and CCTV inspections to measure I&I before addressing problem areas?

While the more information you can get, the better you can develop a long term plan, it is not necessary to do a detailed investigation upfront. More detailed investigations will cost more and you can gather a good deal of preliminary information from treatment plant and pump station flows, operator and field crews experience as well as smoke testing and visual inspections. Having said that, depending on the size and complexity of your network, it can be very useful to collect information from CCTV inspections, 3D scanning and flow gauging to help manage your I/I management strategy. Most water authorities do have a regular CCTV inspection program and with good operators and proper coding, you can develop a good level of knowledge of locations that may contribute to I/I.

Are PRO-RING’s rated for traffic applications ?

PRO-RING has been tested to meet the requirements of Class D trafficable loadings as per AS3996:2019 and detailed in WSA PS 345 "Polymeric Make-up Rings for Sewerage Maintenance Holes".