In the professional communications business, when moisture is an issue
in cables or conduits, we pressurize them. In the building, we inject
compressed air that is passed through a dryer before entering the
conduit/cable. An alternative is to pressurize with nitrogen. Many
times you will see a nitrogen cylinder strapped to a telephone pole with
a hose running to the cable to pressurize it when there has been a leak
in the cable -- a temporary fix until the cable is repaired. We install
pressure gages to monitor for leaks.
Usually, moisture in conduits is the result of humidity and
Hope this helps.
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