I need to detect the in-wall PVC pipes for a central vac system. Apparently one port was covered up with drywall, so the vacuum is broken and the entire system is useless. I cannot find anything for sale or any method that detects PVC pipes with no water in them.
Can you snake a long extension cord through the PVC pipe, run some current through it, and then use a high voltage cable finder to locate the cable in the wall?
Vacuum pipes usually don't have a whole lot of bends in them, so the snaking should be quite simple.
Central VAC lines will be arranged to be connected with minimal turns from the wall port up/down to the main line heading back to the central unit. It may even be that the main backbone of the system is a larger diameter pipe that reduces down to a smaller size at the wall ports.
If this construction exists in your case it should be possible to locate the wall branch pipes in the basement or attic. (Note it can be more of a problem if it is a two story house and the backbone piping is located between floors and feeding to wall ports on both the upstairs and down stairs rooms.
Use a plumbing camera with detector. The camera head puts out a very localized signal. Plus, you can view the camera output to find dead-ends.
If you know the rough location of the outlet take a 4' level and run along the drywall horizontal and you'll see a hump in the wall....this should be the outlet location.