[TowerTalk] Buring Bury-Flex

[Steve Maki]

Sure everyone knows how to glue pipe together, and for short straight 
runs it's easily doable, leaving aside the issue of sealing the ends.

But in longer runs with multiple bends one usually, after looking the 
situation over, elects to do the assembly in the trench. That's where 
the other subset of difficulties begins.

I've done lot's of this stuff on big jobs - just saying it's not a slam 
dunk to get hermetic seals all around, and for the effort involved 
including at the ends...probably not worth it if you're mainly trying to 
protect the cables from crushing forces and to provide the possibility 
of adding a cable or two in the future.

-Steve K8LX

On 5/12/2014 10:10 AM, Patrick Greenlee wrote:
> I'm not sure what a typical ham is but if you aren't physically capable
> of working with the materials then of course you take whatever measures
> you need in order to achieve your goal. If you have the luxury of
> putting the wire/coax/whatever in the pipe before gluing it up then the
> job is much easier.  Run all your cables first allowing a little extra
> at the ends.  Do this with the conduit out of the trench if your
> situation allows as it is usually much easier.  Then start at one end
> and glue the joints one at a time.
>
> PVC pipe is subject to handling damage. Inspect the ends prior to
> assembly and remove any material sticking out so as to interfere with
> assembly or that might "squeegee" off the glue leaving a path for
> leakage. A light buffing with say 220 grit sand paper or similar emery
> cloth on the mating surfaces and the edge of the hole to bevel it
> slightly, yes both the ID and OD mating surfaces and then a quick
> cleaning with the PVC cleaner (comes in can with dauber on lid.) Follow
> the cleaning with priming using the purple primer and then copious
> quantities of PVC cement applied to both the ID and OD mating surfaces
> (don't scrimp... there is no "TOO MUCH" but there is a "TOO LITTLE."
> Insert the male end into the female end (for more detailed instruction
> Google on the words male and female) and push the pieces together while
> turning about a quarter turn or so. Hold the pieces firmly together for
> several seconds as they will act like a lubricated tapered joint and may
> slide partially apart if not held together for a bit.
>
> Not everyone is this thorough and not everyone has problems when not
> this thorough but if you do the above you will not have leaky joints.
> The above is the "BELT AND SUSPENDERS" PVC pipe assembly method. Working
> alone I sometimes use saw horses, pipe stands, and or the pickup
> tailgate to place the pipe up near waist level as kneeling to assemble
> pipe for very long irritates my back condition (degenerative disk
> disease.) If you have something to which you can secure the piece onto
> which you are adding another piece it will make it easier.  Bungee cord
> around a pipe and the cable or folding tailgate lowering mechanism can
> hold the pipe from retreating when you are inserting another piece. I
> fence post driven in at the site to use as a tool for attaching the pipe
> to hold it against the force of adding a length can be handy.
>
> OK, the above will make joints that will withstand as much or more
> pressure as the rating of the pipe (over 100 PSI) and not leak. They
> will also not leak with the single digit pressures at depths we bury our
> hobby cables. Low pressures leak free joints can be had by alternative
> methods. One poster reported using  Vaseline or such.
>
> A quick and dirty but acceptable method is to wipe the surfaces clean
> (it is OK to use a damp rag) then when dry coat the ID and OD of the
> mating surfaces with silicon rubber (RTV)  and immediately shove and
> twist the joint together.  Excess can be layered on the visible joint or
> wiped off., it doesn't matter. You will get it on your hands so have a
> rag to wipe them.  Rubber gloves such as those sold at Harbor Freight
> intended for mechanics (Nitrile rubber) are a good idea. Although this
> silicon rubber method is NOT good for pipes under double digit pressures
> our pressure regime is single digits, most likely under 5 PSI.
>
> As bury flex is good for immersion the only reason to put it in conduit
> underground is mechanical protection.  We have problems with gophers
> eating the insulation off of wires.  Direct bury "Romex" has been
> attacked and destroyed as has buried phone lines.  The only coax I have
> had destroyed by critters was the coax from my Sat TV dish.  It was
> totally chewed up. I always use PVC pipe, either water pipe or Sewer &
> Drain for buried lines.  So far no damage from any source. So far no
> leaks in any of my underground power distribution conduits or ham radio
> related conduits.  I leave a pull cord in all underground runs in case I
> need to pull another wire.  I use these to pull a dry rag or wad of
> paper towel through the conduit to test for moisture.  So far no
> detectable moisture.  I check every 6 mo to a year but may stop checking
> any given run after it has stayed leak free for a few years.
>
> If you can get help with the conduit it will go way easier.  In my
> opinion two guys working with only one hand each can do wire runs in
> conduit easier than one guy with two good hands.  Especially the glueup.
>
> 73,
>
> Patrick NJ5G
>
>
> On 5/12/2014 6:18 AM, Steve Maki wrote:
>> It's not a given that a typical ham (myself included) can achieve
>> consistent plumbing quality seals when working with 10' lengths of 4"
>> schedule 40 in deep irregular trenches and big unruly bundles of
>> cable. And no way to test your work.
>>
>> -Steve K8LX
>>
>> On 5/10/2014 2:21 PM, Patrick Greenlee wrote:
>>
>>> I still don't understand the assumption that the pipe will fill with
>>> water.  Isn't that like assuming the PVC used to deliver water under
>>> pressure will always fail and leak which flies in the face of our
>>> experience?   It doesn't leak in pressure applications over 100 PSI.  A
>>> rough rule of thumb is one PSI of hydraulic pressure for every two feet
>>> of water depth.  If your water depth plus bury depth in your back yard
>>> is say 2 ft  in total then you will have a maximum of 1 PSI of pressure.
>>>    Don't you think a system used successfully to deliver water at over
>>> 100 PSI should be able to take 1 PSI in the rigors of your subterranean
>>> backyard situation?