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Operating a sewer system is a constant battle against water, gravity, and time. Your weapon: a slightly less than heroic budget. With limited budgets, what tools are available for cities to optimize the flow in their sanitary sewers while seeking a return on their investment?

Enter Grouting.

Grouting: Combatting Infiltration

A significant issue in any sanitary sewer is infiltration—which is ground water or sea water entering a pipeline through the pipe joints. Ideally, you want to treat sewage only in the plant, as you don’t want to pay to treat extra flow. 

Some of the negative effects of infiltration include:

• Additional cost to process sewage at the treatment plant
• Costs of wear and tear on pump stations running for longer periods of time, even continuously
• Destabilization of the pipe due to loss of surrounding support

This is where grouting comes in as an effective and efficient tool.

What does grouting do?

Grout seals voids around a pipe with the injection of a multi-component resin through the joint and into its voids to stop infiltration and exfiltration: water flowing in and out of the pipe. Grouting stabilizes the surrounding soil and pipe, seals any open space between the host pipe and any liner, and prepares the pipe for future structural rehabilitation.

Critically, grouting stops leaks at four points of entry: manholes, joints, service line (lateral) connections, and the first few feet of the service line.

How does it work?

Grouting equipment works in tandem with a CCTV inspection system. The recommended process is to test, grout, and verify.

With the visual help of the CCTV camera, a packer is centered over a joint. The packer then inflates and injects pressure into a joint; if the pressure holds for 30 seconds, the joint passes; if pressure doesn’t hold, the joint fails. It’s not uncommon for a joint to fail this pressure test and be considered “bad,” despite the lack of visible infiltration. The packer’s role is crucial. 

Next, the packer reinflates and the grout is injected under pressure into the joint until the joint pressure spikes, indicating that the void around the pipe is filled. Then the packer is reinflated to inject pressure into the joint to ensure the repair is good. Test. Grout. Verify.

Is it cost-effective?

Grouting a pipe is considerably less expensive than relining it or replacing it. A municipality can save expenses across the board: system and equipment wear and tear, pipe stability, and flow to the treatment plant.

In fact, grouting is one of the few trenchless technologies with a measurable return on investment. A municipality will know what normal flow should be and knows the cost to process every 1,000 gallons of sewage. With a dedicated grouting strategy in place, a municipality can estimate the reduction of flow to the treatment plant—and calculate the direct savings. 

Let’s walk through a real-life example: Miami Dade County, which has been running a dedicated grouting strategy for more than 10 years. The county estimates that for every dollar spent on grouting, they save $2.50. This grouting strategy means 128MM gallons of additional flow is no longer flowing to the treatment plant—protecting the county’s equipment and their bottom line. 

With this proven, cost-effective way to seal and stabilize pipes in your sewer system, CUES is dedicated to helping you maintain the value and extend the life of your sanitary sewer.

The CUES team delivers for our customers every day, and we’re ready to go to work for you. Explore our grouting systems.