[TowerTalk] Drip irrigation tubing as conduit, revisited.

[Patrick Greenlee]

Previously I mentioned here that I wanted to use 3/4 inch ID black 
plastic drip irrigation tubing rated for 100 PSI and available for about 
$12 per 100 ft roll at the big box stores like Lowes or Home Depot for 
conduit thinking it would be good for burial or environmental protection 
above ground as it has good UV resistance. I got replies indicating it 
had been tried and failed, especially in longer lengths.

I purchased 4 each 100 ft rolls of the 3/4 inch 100 PSI drip irrigation 
tubing.  I wanted to use it to protect 8 wires, 6 each #14 and 2 each 
#12 that would run underground from a barn to a tower site just under 
100 ft away.  I rolled out one 100 ft section and clamped Vise Grip type 
pliers to each end to facilitate keeping the tubing from rolling back 
up.  I then the ran my electrician's tape through the tubing, attached a 
3 stand polypropylene rope (cheapy from Harbor Freight) and retracted 
the tape pulling the rope through the tuning.

I set up a painters ladder with the backside toward the tubing but a few 
feet away from the end of the tube.  I placed a scrap of pipe through 
two of the rolls of wire and suspended them by tying para cord from the 
axle to the ladder's braces. Note, the ladder rungs are too close 
together to allow free wheeling of the rolls, hence using the backside 
where the braces are farther apart than the rungs. I similarly suspended 
the other two rolls of wire. Four rolls  of two conductor wire.  Three 
rolls are 14 ga and one roll of 12 ga.of wire.  I wove the wire through 
the rope a few (4 to 6) times.  You do this by twisting the rope against 
the lay and it opens up enough to put a wire through it.  I then taped 
the ends of the wire tightly to the rope.

I then manually pulled on the rope while holding the tube with my other 
hand and the 8 conductors (4 pairs) of wire were easily pulled through 
the 100 ft length of tubing,  There was room for a few more conductors, 
I think, before pulling would have become really difficult.  I had a 
quart of electricians wire pulling lubricant standing by but didn't need 
it.  I repeated this process for a total of three irrigation tubes full 
of wires.  My rotators require 8 wires each so this handles two rotators 
and leaves 8 conductors for coax relay switching and winch control for 
crank-up.

I have subsequently pulled the three tubes full of wires plus a 10-2 
with ground direct burial romex through a buried conduit to the tower 
located nearly 100 ft from the barn. I pulled all of this at the same 
time in one shot.  It was considerably more physically demanding so I 
had the only other ham in my zip code mind the bundle as it went into 
the conduit were it exited the barn while I pulled at the tower end. I 
could manage it but it was strenuous so I tied the rope to the pickup 
and slowly drove away. All went fine the second try.  The first try the 
rope pulled through nearly a roll of electrical tape.  Manually removed 
the bundle from the conduit, tied constricting knots around the bundle 
(should have done this in the first place) which get tighter the harder 
you pull. All went perfect on the second try.  Neither the pickup nor 
myself were physically challenged.

This drip irrigation tube in 3/4 inch ID at about $12 per 100 ft seems 
like an excellent way to bury wires if you are not going to try to add 
more conductors after the fact. I don't know, not having tried it but, 
it might be difficult.  With its UV resistance it is a good way to 
weatherproof wires above ground as well, say on a tower for instance. 
Once in place you could seal the openings with RTV or... Something of 
interest I haven't tried yet is to "splice" lengths of tubing together. 
I'm thinking a couple inches at the end of a roll could be heated and 
expanded (belled) just a little to allow mating another section and with 
an appropriate glue and maybe some RTV on top you should have a 
waterproof splice.

Why did I use this tubing for wires in a conduit?  Concern for 
condensation or leaks and because it is cheap insurance, very good 
insurance.  Undoubtedly some of my description of how to will not be as 
clear as I intended.  Send me an email (I'm good on QRZ) and ask 
anything.  I will be happy to try to clarify.

73,

Patrick NJ5G