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Conduit Down Hill

bhackford's picture

Conduit Down Hill (post #205831)

bhackford on Tue, 02/21/2012 - 19:08 (updated 02/21/12 - 02:10) 
in

I have conduit that must have separated.  It is 3 inch and is buried over 24 inches and is URD wire and runs down hill.  When it rains very very heavy, the conduit leaks into the basement.  Panel is the 1st floor, so the water dumps on the basement floor. 

 

The entry into the house is through an LB fitting. 

 

I have read conflicting things about the code for drilling 1/4 holes 18inches up on the entrance conduit and sealing material for the conduit inside effectiviness. 

 

I could dig the pipe up and search for the leak, but lots of digging.  Was looking for the other options. 

 

Thanks

-A +A

Search the 3M website for (post #205831, reply #1 of 5)

by junkhound in reply to bhackford [original] on Tue, 02/21/2012 - 20:28

Search the 3M website for cable seal techniques. 

Used a 2 part epoxy (even on polyethylene) and LM tape to seal Minuteman cables very effectively. 

 

However, that will end up with your conduit filled with water.  Any insulation break in the wire in the conduit will form an electrolytic connection with the water, and eventually the wire will corrode open, then you will need to repull cable or dig.

In addition to physical damage, one of the rationales for NEC not allowing direct burial of NM or THHN, etc.. 

URD would corrode?  What (post #205831, reply #2 of 5)

by bhackford in reply to bhackford [original] on Tue, 02/21/2012 - 21:10

URD would corrode?  What about just putting in a T with a screen?  

Helium, but it's spendy (post #205831, reply #3 of 5)

by Jigs-n-fixtures in reply to bhackford [original] on Wed, 02/22/2012 - 09:43

I've chased leaks on conduit, water, and jet fuel lines with helium, and a helium sniffer. 

This was on an airbase, where you couldn't just start ripping up the ground to find things that were leaking. 

We evacuated the line, and plugged the ends.  Then a mixture of 10% helium and 90% air was injected into the line at low pressure (3 to 5-psi).  You then walked the alignment of the pipe in question with the sniffer.  If it picked up helium you were within a few feet of the leak. 

This works because helium is the lightest and smallest of the natural molecules, and inert.  Which allows it to quickly migrate through soils, (3 thimes faster than air), with out attaching to anything, and get to the surface.  It is also practically nonexistent at the surface of the earth, making it readily detectable even at low concentrations. 

Depending on where you live, there may be a pipeline services company that has the equipment. 

Loosen the cover on the LB to (post #205831, reply #4 of 5)

by sapwood in reply to bhackford [original] on Thu, 02/23/2012 - 09:37

Loosen the cover on the LB to let the water out before it can enter the house.

Underground raceways are (post #205831, reply #5 of 5)

by gfretwell in reply to bhackford [original] on Thu, 02/23/2012 - 21:07

Underground raceways are assumed to be full of water, that is why it is called a wet location. Put in a drip loop before it comes into the house with a hole in the bottom and pack the pipe coming into the house with duct seal.