Key Takeaways

• The SL-RAT screens sewer pipe segments using sound waves, flagging likely clogs without a crew needing to enter the manhole
• A transmitter and receiver work in pairs, one in each of two adjacent manholes, to test the segment between them
• The tool converts signal loss into a simple score, so low-scoring segments can be prioritized for a closer look
• Acoustic screening reduces unnecessary truck rolls, cutting fuel use and emissions tied to routine inspection
• Catching a developing clog early helps prevent sanitary sewer overflows before they become a public health or compliance issue
• Zero-entry screening lowers confined space risk for field crews compared to manhole-entry inspection methods
• RH Borden’s acoustic assessment service applies this same screening approach, then ties the results into a GIS dashboard alongside manhole condition data for a single, prioritized view of system health

The Sewer Line Rapid Assessment Tool (SL-RAT) screens sewer pipes for clogs by sending sound waves through them, letting crews find blockages in seconds without entering a manhole.

BEND, Ore. (KTVZ) — Have you been hearing music in your pipes? It’s not your imagination, or a noisy neighbor. It’s the city of Bend’s new climate-conscious effort to help clear any sewer line clogs.

The Sewer Line Rapid Assessment Tool (SL RAT) plays loud music to determine if pipes are clogged.

“It’s a tone that once you hear it, it’ll stick with you,” said collections system supervisor Justin Young, “But it’s got a musical tune to it. It can be very apparent. It’s no secret that there’s noises going through the sewer lines.”

A transponder is placed in one manhole, and emits the sound waves through the sewer lines. The receiver at the other hole takes the sound waves and calculates them into a score to determine if there’s a clog.

How the SL-RAT Actually Works

The Transponder and Receiver Setup

The basic mechanics behind Bend’s “musical” pipes are simpler than they sound. A technician places a transmitter on  one manhole and a receiver into the next manhole. The transmitter sends an acoustic signal, essentially a controlled sound wave, through the air inside the pipe. The receiver picks up whatever makes it to the other end.

Open, clear pipe lets the signal travel through with very little loss. A blockage, root intrusion, or heavy sediment buildup absorbs or scatters part of that signal, so the receiver gets a weaker, muddier version of what was sent.

Reading the Score

The tool converts that signal difference into a simple numeric score. A high score generally means the segment is flowing freely. A low score flags a pipe that likely needs a closer look, whether that’s a CCTV camera inspection, jetting, or a repair crew.

This is the part that makes the SL-RAT valuable for a city like Bend. Instead of sending a crew to physically inspect every segment on a fixed schedule, staff can screen dozens of segments in a single shift and only dig deeper on the ones that actually score poorly.

Why Acoustic Assessment Matters for Climate-Conscious Utilities

Fewer Truck Rolls, Lower Emissions

Every unnecessary inspection means a truck out on the road, equipment running, and staff hours spent on a pipe that likely did not need attention in the first place. Screening tools like the SL-RAT cut down on that wasted travel by telling crews in advance which segments are worth a closer inspection and which ones can wait. For a city actively branding this as a climate-conscious initiative, that reduction in unnecessary field visits is a real, measurable piece of the story, not just a marketing angle.

Catching Clogs Before They Become Overflows

A clog that goes undetected long enough can back up into a sanitary sewer overflow, which means untreated wastewater reaching streets, waterways, or private property. Beyond the obvious public health and environmental risk, an overflow event also means emergency response costs, reporting obligations, and potential fines that a proactive screening program is specifically designed to avoid. Acoustic assessment is not just a convenience upgrade. It is a frontline tool for preventing the kind of event no utility wants to explain to its ratepayers.

A Zero-Entry Safety Advantage

Traditional pipe inspection sometimes still requires a crew member to physically enter a manhole, which brings confined space risks: limited oxygen, toxic gas buildup, and difficult emergency extraction if something goes wrong. Acoustic screening from the surface removes that exposure.

How RH Borden Applies This Same Approach

Bend’s experience with the SL-RAT lines up closely with the acoustic assessment work RH Borden performs for municipal collection systems across the country. RH Borden’s acoustic assessment service is built around the same core idea Justin Young describes here: screening long stretches of pipe quickly and without confined space entry, then using that data to prioritize the segments that genuinely need attention.

Where RH Borden’s approach goes a step further is in what happens after the acoustic score comes back. Rather than treating each screening result as a standalone data point, RH Borden ties acoustic findings into the same GIS dashboard used for manhole condition data, so a utility’s engineering team sees pipe segment scores and manhole defects on one map instead of two separate reports.

That combination matters most for utilities trying to build a defensible, condition-based maintenance plan rather than a reactive one. A low acoustic score on a segment near a manhole already flagged for structural defects is a much stronger signal than either data point on its own, and it is exactly the kind of pattern a unified dashboard is built to surface.

What This Means for Your Utility

If your collection system is still relying on a fixed inspection calendar rather than condition-based screening, Bend’s example is worth paying attention to. The same acoustic technology behind this story is available to mid-size and large utilities looking to reduce unnecessary field visits, catch problems earlier, and build a data trail that holds up when it is time to request capital funding.

The practical next step is usually a pilot: screening a representative section of the system, comparing the acoustic scores against known problem areas, and using that comparison to build the business case for a wider rollout.

                                                                                     Read More

Bringing Data-Driven Clarity to Every Clog

Bend’s approach shows how a simple idea, listening to a pipe instead of guessing at its condition, can meaningfully cut costs, reduce emissions, and prevent overflows before they start. That same logic is at the center of how RH Borden approaches collection system management: screen fast, prioritize honestly, and put every result somewhere the whole team can actually see and act on it.

Ready to bring this kind of clarity to your own collection system? Visit rhborden.com to learn more about RH Borden’s acoustic assessment and condition-based maintenance services, or reach out directly to talk through a pilot program for your system. Contact us now!

Frequently Asked Questions

What is the Sewer Line Rapid Assessment Tool (SL-RAT)?

It is an acoustic screening tool that sends a sound signal between two manholes to quickly identify whether a pipe segment is clogged or flowing freely.

Does using the SL-RAT require entering the manhole?

No. 

How accurate is an acoustic score compared to a camera inspection?

The two processes are not comparable. An acoustic score is an objective number from 0-10, while a CCTV inspection is a subjective exercise where an operator documents defects and structural features of the pipe. A low acoustic score tells a utility which segments deserve a closer look, often with a camera, rather than replacing that inspection entirely.

Why is this considered a climate-conscious approach?

Screening pipes acoustically reduces the number of unnecessary truck rolls and camera inspections, which cuts fuel use and emissions tied to routine collection system maintenance. The average system replaces 89% of their cleaning with acoustic assessment.

Can acoustic assessment data be combined with other condition data?

Yes. Acoustic assessment is just one powerful tool in the kit of sophisticated sysytem operators. It focuses cleaning, CCTV, and rehabilitation efforts on those assets that really need it.