Acoustic Inspection Receiver

An acoustic inspection receiver. 

New Castle County will soon deploy acoustic inspection technology to detect sewer line blockages. It detects sewer line blockages through sound waves, and can help workers find and clean blockages before a sewage overflow.


The way it works is workers place a transmitter over one manhole, and a receiver over another manhole a short distance away that’s connected by the same sewer line. Then the transmitter sends sound waves, the receiver receives it and runs through a number of algorithms. Based on the distance between the transmitter, and what it hears, it develops a score. Zero means the line is completely blocked. Ten means it’s completely clear.

It will allow the county to focus its resources on lines that need attention.

“This specific technology allows us to determine whether sewer lines need to be cleaned or not,” said County Operation Services Manager Robert Roff. “Right now when the county goes into a neighborhood to clean the collector system, we clean every single line segment.”

With the acoustic inspection technology, crews won’t have to waste time cleaning lines that don’t need to be cleaned. Not only does it save money, it also is more efficient.

“So we’re hoping to,” said Roff, “incorporate it into our existing program to be able to reach more of the county collector system each year. A combination of the acoustical testing and cleaning.”

County Executive Matt Meyer said, since the county began in 1673, the number one thing it has done for the public health, safety, and welfare is provide a quality underground sewer system. This new technology, he said, will make the system more cost effective, efficient, and safer.

“Anything that prevents us from going down into the manholes unnecessarily is more efficient for the taxpayer,” said Meyer. “It’s also just a really neat technology that enables us to detect problems in our sewer system much quicker. So we can focus our resources on those sewers that need the help the most.”

More than half of the blockages in the county are caused by people pouring fat, oil, and grease down the drain. Environmental Compliance Manager Michael Harris said this tool will help.

“This is a tool that we can use to screen the sewer quickly and to see if it has potential for a blockage,” said Harris. “And we can react quickly and get it cleaned so it doesn’t cause an environmental problem.”

Harris urges people not to dump fat, oil, and grease down the drain. Not only can it cause your plumbing to back up, but it causes big problems for the county.

“Just take a little extra time,” said Harris, “wipe the oil and grease off your plate before you put it into the dishwasher. If you’re cooking, if you have oil and grease in a pan, just let it cool down a little bit. Put it in a can, put that can in the refrigerator, let it cool down then throw it in the trash. Keep it out of the sewer.”

There is a public education outreach campaign called Great Schools Clean Streams running until April 20th. Harris encourages people to visit the website.

Fat, grease, and oil may cause the most blockages, but there are other things that can block sewer lines as well. The acoustic technology detects all blockages.

“Any types of roots, or grease, or debris, it’s going to pick it up and it’s going to slow the sound waves down,” said Roff.

The county has a number of programs it has used to decrease those other blockages.

“Since 2009 we’ve lowered our sanitary sewer overflows by 77%,” said Roff.

He said the acoustic technology will be used to target areas known for grease, oil, and fat stoppages. The county has been doing pilot testing of the acoustic technology for about a year. 

I'm a Texan who worked as a TV reporter for two years at KFDM Channel 6 News in Beaumont. Hook 'em horns! I graduated from the University of Texas at Austin with a bachelor's degree in broadcast journalism and a minor in government.