... the electricians wanted to know why their conduit "leaked" in wet locations more than it did before.
Even the standard tapered NPT leaks. The way the thread was designed in the 1800's, there is a small gap at the top of the threads, which always results in a helical leak path. That is why pipe dope or Teflon tape is always required with NPT plumbing joints. (I note that there exist other threads that seal without the need for a sealant.)
