Rainwater often flows into sewer pipes through incorrectly connected drainage on private properties. The plumbing of spouting on the roof, and drainage pipes from rainwater tanks, are common causes.

Also, some backyards are landscaped on a slight slope to help with drainage, and sometimes this sends rainfall flows into a property’s Overflow Relief Gully.

Additionally, sewer pipes can be damaged by tree roots, or become cracked due to ground movement and old age, and this can allow water to get in.

An Overflow Relief Gully (ORG) is a fitting located just outside a house's wall, and it prevents sewage from spilling inside the house.

If a sewer becomes blocked, the sewage flows will spill out of the ORG instead of inside the house.

It is important that ORGs don’t get covered or blocked, and that drains from properties don’t let water flow into the ORG.

Yes, sewers are designed to be a certain size that is appropriate for their area. When rainwater enters the sewer, and if flows within the pipes become too big, there is a risk of sewage spilling into the environment.

These spills usually occur from sewer manholes located at low points in the sewerage network.

Yarra Valley Water regularly monitors the levels of flows within our sewer pipes. We found that the Ringwood area had much greater flows when it rained, compared to during dry weather, and therefore suspected that rainfall entering our sewer pipes was a significant issue in the area.

Properties included in the trial were located within a small area that was identified as having a lot of rainwater entering the sewer.

By inspecting these properties, we were confident we could identify where rainwater was entering the sewer.

The inspections were done by our contractor, Veolia.

Veolia specialises in the maintenance of wastewater collection systems and is a long standing partner of Yarra Valley Water.

Veolia looked at the drainage pipes from things such as rainwater tanks and rain gutters, to make sure everything was properly connected.

Veolia also inspected the condition of the underground pipe running between the property and the larger sewer pipe in the street.

Our contractor, Veolia, carried out inspections between February and June 2015. They identified a number of properties with plumbing that contributed to rainwater flowing into the sewerage system.

However, flows from these properties with non-compliant plumbing into the sewerage system were less than we expected to find.

Yes, rectification works were carried out on properties with non-compliant plumbing to ensure the Ringwood trial area has compliant plumbing connections.

Usually, the cost to undertake rectification works to achieve a compliant plumbing standard would be paid by the property owner. However, as part of the trial, the rectification works were carried out by our contractor, Veolia, and were paid for by Yarra Valley Water.

We commenced plumbing works in March 2016, and these were completed in late June 2016.

After completing the rectification works, we monitored sewer flows in the area during heavy storms.

We’ve finished our monitoring and it showed that the inspections and plumbing rectification works achieved a significant reduction in the flow of rainwater into the sewer, and therefore reduced the likelihood of sewer spills occurring during heavy storms.

We were hoping however that the trial would have a greater impact on the performance of the sewerage system, like what would be achieved through our usual approach – construction works to upsize the sewer pipes running through the neighbourhood.

We also found that arranging for property inspections and repairs had a higher direct impact on our customers than was desirable.

We are committed to reducing rainwater flows into the sewerage system.

Besides the rectification works that were performed for non-compliant properties, which ensured all trial properties have compliant plumbing, we installed leak-resistant covers on sewer manholes located in the area.

The new manhole covers are specially designed to prevent rainwater flows from entering the sewerage system by sealing the manhole lid with a rubber gasket.

The manholes are located in Ringwood's public open spaces, within road surfaces, and sometimes in the backyards of private properties.

The leak-resistant manhole covers were installed in late 2015.

Yes. The Water Act 1989 gives us the authority to enter private properties and conduct inspections to access and perform works on sewer manholes.

It's unusual for us to need to come onto properties unless we are carrying out routine maintenance. However, this trial project was important to help us to reduce rainwater flows entering the sewer. Where we needed to enter properties, we contacted property owners in advance to let them know.

We trust that property owners understood our position, and we thank them for their cooperation.