A central source for insights, tools, and updates on acoustic sewer inspection technology, wastewater infrastructure assessment, and cost-effective solutions for municipal inspection services and collection system optimization.
Our technology relies on the fact that sound traveling through air mimics the flow of water through a pipe. We use an active transmitter – think of it as the part “yelling” down the pipe, coupled with a receiver – the “brain” that uses sophisticated algorithms and a patented process to interpret blockages based on what it “hears” coming through the pipe.
The SL-RAT can provide a blockage assessment 10-20x faster than CCTV, for less than 1/10th to 1/20th the cost per foot, and without the need for pre-cleaning or contact with the waste flow. The SL-RAT is best for quick and low-cost screening of small diameter pipes, but is limited to pipes under 18 inches in diameter. On the other hand, a zoom camera’s sight distance is greatly limited by small-diameter pipes. To see a comprehensive comparison between pole (zoom) cameras, CCTV and SL-RAT technologies, click here.
We have found on average the device costs less than $0.10/foot ($0.30/m) for inspection – including a two-person crew and a service vehicle. Operating costs depend on labor rates and productivity and can vary from $0.05/ft to $0.15/ft ($0.15/m to $0.50/m).
It measures the dissipation of sound energy through the airspace within the pipe between the sewage flow and the pipe wall. The more aggregate obstructions within the pipe – such as roots, grease, debris, joint offsets, “hammer tap” lateral connections, etc. – the more the sound energy is blocked. Our device measures this “energy gap” and then develops a blockage assessment. The assessment uses a proprietary algorithm based on a statistical model of sound behavior in conduits that was developed through several years of empirical research in sanitary sewer lines.
As the free space in the pipe becomes more constricted by the water flow so will the acoustic signal used to measure the available excess capacity within the pipe. Simply put, as the water level increases above 75%, the blockage assessment will tend to decrease until at full pipe the assessment is zero. That being said, our experience has found it very rare to have a small diameter gravity-fed sewer pipe that continuously remains in that flow volume range – when that is occurring it typically points to pipe capacity issues which the SL-RAT® can indirectly detect.
The SL-RAT® is a rapid assessment tool that is designed to quickly identify “problem” segments. Once a blockage is detected with the SL-RAT®, a more detailed method such as CCTV should be focused to learn more details about the potential problem.
The SL-RAT® is tuned for use in 6 -12″ (150mm-300mm) diameter unpressurized collection pipe with a flow-level capacity at measurement that is below 90% of capacity. Since the SL-RAT® uses sound energy to detect blockages, it can go around turns and flow over obstacles – unlike CCTV. The type of pipe does not matter –although clay pipe with significant joint offsets will typically generate lower acoustic scores relative to other types of pipe such as cast iron and PVC.
The measurement algorithm has been designed to be conservative, i.e., if it errors, it will declare a pipe to be more obstructed than it actually is. This has been proven to be the case in head-to-head comparison studies with CCTV and the SL-RAT® acoustic inspection. The beauty of the design is that obstructions that block water flow also block sound.
Depending on ambient noise levels, our customers have obtained measurements reliably up to distances of 800 feet (240 meters).
The recommended pipe diameter is 6 – 12″ (150 to 300mm), and the scoring algorithm is based on this range of pipe diameter. It is possible to use the technology up to 30″ (750mm) in diameter, but it is not recommended, and should only be used when other inspection methods are not available. Also, at larger diameters, it is important to establish a baseline acoustic score and then look at variations, rather than solely relying on the score obtained.
The devices use a high-quality GPS chip, which is nominally rated for +/-15 feet (5-meter accuracy). Practically speaking, we do find the accuracy can be lower than you would typically see in a handheld device due to the SL-RAT®’s proximity to the ground and the fact that the chip is located inside a weather proof box. In certain situations, it is possible to see significant errors in the GPS readings (100 feet or more), so we recommend writing down the asset ID or marking test locations with SL-RAT measurement ID and acoustic score on a map or handheld device while making acoustic measurements.
The SL-RAT® is designed to operate in pipes with lateral connections, even in residential areas. An excessive number of lateral connections, especially capped laterals, can reduce the amount of sound energy that reaches the receiver, hence resulting in a lower acoustic score. Additionally, more sound will “leak” up larger laterals so scores may be slightly lower in sewer lines that connect to 6″ (150mm) laterals versus the more standard 4″ (100mm).
The blockage assessment resolution (0 to 10 scale) has been well matched to the measurement repeatability and accuracy. More technical information is available upon request.
Both the receiver (RX) and transmitter (TX) use a lithium-ion battery, similar to a laptop battery but with a higher rate of discharge. Both devices have the same battery, the TX device uses the most power and is rated for approximately 50-80 measurements per battery charge. In terms of overall battery life, we expect the batteries to last several years (the batteries are replaceable). The RX unit uses very little power by comparison, and can last up to a week on a single charge.
Devices can be purchased, rented, or leased. Purchased devices include a one year limited warranty and the option to subscribe to our SL-DOG® software package. In addition, there are many contractors that can perform acoustic inspections as a subcontracted service.
An assessment of pipe blockage for a sewer line segment is typically attained in less than 5 minutes after the manhole covers are removed. The actual measurement time is between 1.5 to 3 minutes, depending on the number of test cycles the device performs (this is done automatically). A two-person crew can typically inspect 50-60 segments, averaging 8,000 – 10,000 feet (2,500 – 3,000 meters) of pipe per day independently, and without the need of a cleaning crew for support. Depending on topography, traffic control needs, and the ease of finding manhole lids, our customers have found it possible to inspect up to 6 miles (9000 meters) per day.
If the receiver (RX) is unable to hear because of excessive background noise such as passing train or major highway traffic, it will indicate “NOISE” at the end of the test. This is a rare occurrence, and is usually corrected by switching the positions of the RX and TX unit, or by running the test at a time when the background noise is lower.
Our customers typically use a dedicated two-person SL-RAT® crew to quickly assess a subdivision or basin for dirty segments and blockages. The assessments can then be used to focus on the specific “problem” segments for further detailed CCTV inspection, repair, or cleaning. Our customers have found that the SL-RAT tool can typically focus cleaning activity in most basins to less than 50% of the segments while not degrading SSO performance.
No. The transmitter (TX) operator is exposed to 85 to 88dBA for 3 seconds during each tone sequence. Even during the heaviest work day this equates to approximately 24 minutes total, 10.6 hours are permitted by OSHA standards. Additional documentation on this is available upon request. That being said, most operators like to wear ear buds as listening to the repeating tones can become monotonous.
Yes. The devices are designed to be used outdoors in the rain. We do not recommend submerging the units, but they are sealed and weatherproofed, so they can be splashed with water. They are also rated for operation from 0 to 140° F (-18 to 60° C).
The recommended method of inspection is to have the receiver (RX) and transmitter (TX) on adjacent manholes. There are some exceptions to this. If a manhole cannot be accessed or located, it is possible to obtain an acoustic score for 2 segments, but it is likely a lower score will occur due to sound energy dissipated in the intermediate manhole. Also, if the RX and TX unit are “close” to each other (within 50 feet or 15 meters), then it is recommended to obtain one measurement for the short segment, then another acoustic measurement with an intermediate manhole in between.
The results are available to the user at the time of testing and should be recorded on a map, work order, or inspection log. The device stores the most recent 500 measurements. Measurement data can be downloaded free of charge using the Sewer Line Diagnostic OrGanizer (SL-DOG®) PC client. This requires a Windows PC, internet connection and a USB port. The data format is a comma delimited text file (CSV) that can be opened in Excel. Included are data such as measurement ID, time stamp, assessment score and GPS coordinates. There is no charge for the PC client software or downloading the raw CSV file from the SL-RAT® device.
There is no need to take the line out of service when making measurements. In other words, the SL-RAT® does not impact normal collection system operations.
It is possible to “inchworm” or “leapfrog” from one segment to the next. We recommend the “inchworm” method, each operator advances their device to the next manhole after a measurement is performed, rather than one operator staying stationary and the other operator skipping over them to the next manhole (“leapfrog”). The data are easier to process and manage when collected in this fashion.
A drop manhole can reduce the overall score, especially if it is an intermediate manhole. Recommended operation is to have the transmitter (TX) placed at the drop manhole.
The blockage assessment is primarily based on the air gap above the flow. The assessment can be impacted by debris under the flow, if the debris causes a “bump” or splashing water in the flow or in the case of sediment if it causes a rippling effect in the water. If the sediment level in combination with the wastewater flow above it leads to a pipe that is in the range of 75% or more full, then the SL-RAT® score may be lowered (see question on “Free Space” above for more detail on this aspect). That being said, the SL-RAT does not see below the water level and will not directly estimate the amount of sediment or debris in a sewer line.
Possibly. Sound levels are not a concern from a safety perspective, but if there is a dry trap or connected air space from the mainline through the lateral, it is possible that the tones could be heard. This is quite a rare occurrence.
If the receiver (RX) and transmitter (TX) are within 50 feet (15 meters) of each other, it is possible that a higher acoustic score could be due to hearing the tones over the air, instead of through the pipe. The device is designed to issue a cautionary warning that this could be occurring. If there are GPS or intradevice communication issues due to the environment, this could occur even when the devices are farther apart. If you receive a high score and the devices are within 50 feet of each other, then it is recommended to obtain one measurement for the short segment, then another acoustic measurement with an intermediate manhole in between.
No. We have run tests to depths of 35 feet (12 meters) and found no appreciable loss in measurement quality.
No. While technically possible this would require an additional device and person, and the equipment is not setup to handle multiple receivers. In practice, the inspections are completed so quickly that our customers have found very few practical field situations where it would make sense economically to use multiple receivers with one transmitter.
Go directly to www.sl-dog.com to access the login page.
If you can’t remember your SL-DOG log-in username or password, please email techsupport@infosense.com
Access to the SL-DOG requires a Microsoft Windows-based PC using (XP, 7, 8, or 10) and a supported web browser (Chrome or Internet Explorer). Please note, the SL-DOG is not supported by Firefox at this time. Users also need a standard USB cable (provided with the SL-RAT), an active internet connection, and log in credentials.
The SL-DOG web portal allows users to organize, archive, view, report and visualize the data for all the downloaded SL-RAT measurements they have conducted. A measurement filter page allows users to filter for specific measurement data based on scores, notes, or proximity. Notes can be added to each measurement, and the GPS coordinates can be edited for accuracy. Measurement data can be exported as a CSV, KML, SHP or PDF files for easy integration with other enterprise systems such as ArcGIS, Cityworks, Cartegraph, Hansen, and Lucity.
The Sewer Line Data OrGanizer is the only data management software specifically designed to help manage SL-RAT acoustic assessment data. The SL-DOG ensures that all uploaded data is securely archived for future access, and is essential to creating daily verification reports and summaries, which is the protocol in the ASTM Standard, “Standard Practice for Prioritizing Sewer Pipe Cleaning Operations by Using Transmissive Acoustic Inspection.”
You will need to install a desktop app (System Setup) and USB Setup, which can be accessed through the SL-DOG Portal’s Support Docs page. Installation instructions can be found in your SL-DOG web portal in the SL-DOG Quick Start Guide, located in the same Support Docs page. Once all installations have been completed, the user can connect the SL-RAT to the PC using the provided non-proprietary USB cable and upload measurements.
For further assistance, this recorded webinar discusses the overview of SL-RAT data management features, including how to upload measurement data. To see the steps for ensuring data upload, click here.
The first year of access is provided as part of your SL-RAT purchase, rental, lease or subscription., At the expiration of the first year, access tothe SL-DOG portal requires a paid subscription. This fee can vary depending on how many active SL-RAT devices are supported in your portal. There is no individual seat license for using the portal and both the mobile App and the local download software remain free. Please reach out to sales@infosense.com for questions about SL-DOG portal renewal quotes.
Once you upload your SL-RAT data to the portal, this data will be saved indefinitely. Even if your portal expires, all data that has been uploaded in the past, or uploaded to the expired portal using the desktop app (local client), will be stored for future access. Please note, the data does not automatically upload to your web portal, the user must manually upload the data from the SL-RAT device using the desktop app (local client) and USB cable. To see the steps for ensuring data upload, click here.
Definitions of terms can be found in the SL-RAT User’s Manual (pages 25-27). Also, users can hover over the text in the column headers in the web portal to see the definition of each term.
For data integrity, acoustic assessment data cannot be permanently erased or deleted from the database. However, users can select measurements to “hide” or filter the data for specific criteria using the “Measurement Search” capability.
You can download your SL-RAT measurement results in the following formats: CSV (Excel), SHP (ArcGIS), PDF or to KML (Google Earth).
Example reports are provided in the SL-RAT User’s Manual for CSV (page 29), KML (page 30) and PDF (page 31) reports. For SHP file exports, we recommend viewing the following video.
There is a mobile app that allows operators in the field to add a variety of details to the data being collected. Please see this recorded webinar on the mobile app, or see the Quick Start Guide provided in your SL-DOG portal under Support Documents for more information on how to use the mobile app to do this.
As a second option, the same information collected using the mobile app can also be entered directly in the SL-DOG portal after the data is downloaded – if the field operators are manually documenting information while in the field.
One way to integrate acoustic data into existing systems is to associate a unique segment ID to the measurements that can be referenced for associating the data. This can be done using the mobile app or the web portal – this video shows you how to add this field to your measurement data using both methods.
If you are looking for a more specific integration need, please reach out to our team by emailing techsupport@infosense.com.
For an overview of how to work with SHP files using SL-DOG, see this video.
As with any other data collection process, he assessment scores should be reviewed in conjunction with other data collected during the testing process to ensure accuracy and quality. Some examples include looking at the “Measurement Status”. If the Measurement Status does not say “Valid”, the assessment should be further evaluated for reasons such as lack of synchronization of component operation by the field crews during a test. This can lead to “Early”, “Late” and “No TX” flags in the database. Or, if GPS accuracy needs to be edited to provide a better re-assessment of the acoustic scoring in the web portal. Additionally, comparing the Field Assess with GPS Assess scores can be a helpful way of seeing whether operator evaluated pipe lengths are consistent with GPS determined length of pipe. Inconsistencies between operator and GPS calculated scores are highlighted in orange to flag them for further review. Additional verification checks can be performed such as ensuring asset ID’s are properly included, etc.
This QC step can also highlight the need for operator training where errors such as those described above occur more systematically.
The SL-DOG mobile app is a free app for iOS (Apple) and Android mobile devices such as tablets and smart phones. The app allows operators in the field to add notes to the data being collected. Please see this recorded webinar on the mobile app, or see the Quick Start Guide provided in your SL-DOG portal under Support Documents for more information on how to use the mobile app.
The SL-DOG mobile app can be downloaded for free for iOS or Android devices at their respective app stores. Search for “InfoSense SL-DOG” to find the app and download to your device. To log into the app, use the same credentials as for logging into the SL-DOG portal.
The mobile app can be a convenient way of associating meaningful notes and data with acoustic assessment results, in real time, while the operator is in the field conducting the tests. Data such as segment ID, manhole ID, or Basin ID may be helpful for reporting purposes, or for connecting and integrating the SL-RAT data into other existing systems. Notes can be a helpful way for operators to immediately and definitively write any observations in the field that need to be addressed. Examples of field observations could include descriptions such as “right of way needs to be cleared”, or “manhole shows evidence of I&I”, or “this asset is not in our GIS system”.
