Many wastewater collection system technicians have had this experience: You need to inspect a line, or set up a skid for waterjet cleaning, but from your vantage point in the street you can’t confidently tell if the pipe is 6-inch or 8-inch. And you’d rather not perform a confined-space entry to go down the manhole and use a tape measure.

Trent Tobiason, a sewer maintenance worker for the City of Columbus, Neb., faced such issues often — and developed a solution. “It’s a simple device that can be built with about $10 to $15 in parts from a hardware store,” he says.

The tool (see accompanying pictures) is made of plastic pipe. The long vertical piece and the short coming off at 90 degrees are 3/4-inch Schedule 40 PVC. The two short pieces coming out the ends of the tee connector are Schedule 30 PVC pipe. The piece slid through the Schedule 30 PVC is 3/4-inch CPVC.

Tobiason cut slits in the Schedule 30 sections so the hose clamps can squeeze and hold the CPVC piece. Then he cut pieces of CPVC about one-half inch shorter than the standard inside diameters of various-size sewer pipes: for example, 5.5 inches for measuring 6-inch pipe, 7.5 inches for measuring 8-inch pipe.

Now, suppose he believes — but isn’t certain — that a pipe at the bottom of a manhole is 8 inches. He inserts the 7.5-inch CPVC section to the tool, clamps it in place, and inserts the tool down the manhole. He then tries to move the 7.5-inch measuring piece into the pipe. If it won’t fit, he knows that pipe is smaller than 8 inches, and he can measure again with a different piece of CPVC.

If it does fit in the pipe, he checks side-to-side and up-and-down movement, keeping tool square with sewer main. If tool has sloppy fit, he knows the pipe is larger and tries the next longest CPVC section.

“Be sure not to measure the bell of a main,” he says. “To have additional verification of the pipe size, you can insert the tool and use a pole-mounted camera to get a visual. This method sure beats climbing down inside a manhole.”