Coax cable ?

[Shadetree Mechanic]

If the pipe ends are sealed, how does new moist air get in to condense?

 

[FlatlandBusa]

If the pipe ends are sealed, how does new moist air get in to condense?

Unless it is 100% air tight, the pipe will breathe a little bit and pull humid air in which condenses. It's almost impossible to make a pipe with a cable pass through 100% sealed.

 

[Captain Kilowatt]

If the pipe ends are sealed, how does new moist air get in to condense?

Temperature and humidity changes along with changes in atmospheric pressure all work to create condensation. I had a four inch PVC pipe loaded with many cables. It ran slightly downhill to the tower and then about three feet up to a 180 degree bend at the top to keep water out. One day I noticed the ground was damp at the tower base despite it being midsummer. The PVC pipe had filled with water was was slowly dripping out. I drilled a very small hole at the base and drained the water out. The water was crystal clear proving it was not just ground water infiltration. It is basically impossible to seal a pipe with cables in it tight enough to never cause an issue. One guy I knew even ran a small fan on one end to create airflow thinking he would not have a problem. He was wrong and it filled with water anyway. The Cushcraft 13B2 antenna has a sealed box at the feedpoint. Almost every one of them had problems with water. those that drilled a small weeping hole before installing it had no problems.

 

[AudioShockwav]

Yep, even very small air leaks allow humid air to move in and out of a pipe as they heat and cool.
This will condense into water after a while, it happens.
When we expanded the plant I was working at in the early 80's we ran long runs of big conduit there, much of it 4"
About 18 months later we had to pull another run of power and control wires for A big vertical screw press.
There was already water in the conduit.
It just happens.

73
Jeff

 

[Shadetree Mechanic]

That is good to know, I was thinking about running my wires in the flexible 2 inch black polyethylene water pipe. When I bury it, I will have it slope down in the middle and put a hole in the bottom. Thanks guys.

 

[secret squirrel]

To tell you the truth. Last time I buried cable for my current antenna setup, I just used RG-8 put together at Bob's CB and ran it inside 2 inch PVC drain pipe. I put on upside Us, or traps in order to keep out the rain. Nothing complex. My logic was if this fails after a few years, then i will get direct burial cable and try again with version 2.0. oh and what the other said. be sure to make sure there is some downhill slop with a drain to let moisture out that accumulated. We all discuss doing everything perfect, but important is to work with what you have available and enjoy your work.