[TowerTalk] TowerTalk Digest, Vol 122, Issue 58

[K8RI]

On 2/28/2013 10:38 AM, Patrick Greenlee wrote:
> Lots of opinions and no consensus.  Typical.
>
> I didn't have nary a drop of water in my 3 inch conduit 6 months ago but
> I will check again because of all the folks who think all buried
> conduits have water.

It's not that all buried conduit will have water, it's just most any 
buried conduit is likely to get water at times.

Presently mine which is shallow enough to be in frozen earth and open on 
both ends with none of the joints glues doesn't have ant water standing 
in it,  T%here are NEMA BOXES  on each end, There is about a 6" stub 
through the end plate into the basement.  As on end is into the fairly 
warm basement, this is a prime location for condensation and frozen 
droplets.  There is none at present and pulling out 4 or  5 feet of pull 
line shoes no moisture.  Due to the heating system in the house this 
tends to have a negative pressure causing a slight flow into the basement.

The pull rope will show moisture in the spring when the relative 
humidity is high, but "so far I've never found liquid water.

Very cold air enters through the fittings in the large box at the base 
of the tower.. even in the frozen ground it is warmed a little above the 
outside air temp. which reduces the relative humidity.  In the spring 
warm, humid air enters at the tower and is cooled which raises the 
relative humidity which will cause condensation.  As the ground warms 
with the onset of warm weather this condensation will evaporate.  The 
typical time for there to be condensation in the conduit is 4 to 6 weeks 
although there a few times in late spring, early Summer, or fall when 
conditions may be right for a few days.

It'd be interesting as to how much cross flow there is between the 
basement and shop as the conduits have the box at the base of the tower 
in common.


A dry air purge through the conduit dry but is it worth the effort?
http://www.rogerhalstead.com/ham_files/cablebox.htm shows the history 
and what I have from the basement to the tower as well as from the shop 
to the tower.

Originally I had a 5" sewer pipe from the tower to the basement with a 
"Y" just before entering the basement. One leg of the "Y" was down and 
capped. The cap had some small holes for drainage if necessary. Almost 
the entire run is in the sand back fill around the basement.  There is a 
weep tile at the bottom so the sand is always dru excep when it's 
raining and then the water just drains down through the sand.

The run from the shop to the tower is basically below the watwe table in 
the spring, but it's open on each end.  I've not had problems with water 
in it, but I don't think it'd be a problem were it to be filled with water.

I can see where water can be a big problem with direct burial coax, but 
not with coax in conduit unless it's there when you wish to pull cables 
in or out.

73

Roger  (K8RI)