# Trick for preventing PVC conduit pulling apart?



## papaotis (Jun 8, 2013)

#1 do not disturb for an hour after gluing. #2 glue it right, make sure it fits right, make sure it it in all the way.


----------



## MechanicalDVR (Dec 29, 2007)

An expansion coupling? Compressing (tamping) the ground under the sweep is also a good idea.


----------



## frenchelectrican (Mar 15, 2007)

mike9666 said:


> Did a underground PVC run and it pulled apart right where it comes up from the ground after the ground had settled. Is there a trick that i missed?


A very common trick .,, 

A expanding conduit which it will have sleeve over conduit so when the ground shift some it will not let it pull out apart.,,

and leave some slack on the conductors after you get it fix if you can.


----------



## papaotis (Jun 8, 2013)

you an expansion coupling frenchie?


----------



## Southeast Power (Jan 18, 2009)

mike9666 said:


> Did a underground PVC run and it pulled apart right where it comes up from the ground after the ground had settled. Is there a trick that i missed?


What size pipe was it?


----------



## jw0445 (Oct 9, 2009)

You need to use a sufficient amount of glue, then hold it pushed in for about 5 - 10 seconds until the glue sets. After that if you don't use a slip riser it will pull off the wall if the ground settles.


----------



## 99cents (Aug 20, 2012)

You apply cement to both the pipe and the fitting and after you put it together, you give it twist. You should put a sleeve over top where it comes out of the ground. That's particularly critical when they're going to pour concrete afterwards. It's good practise anyway.


----------



## Signal1 (Feb 10, 2016)

jw0445 said:


> You need to use a sufficient amount of glue, then hold it pushed in for about 5 - 10 seconds until the glue sets. After that if you don't use a slip riser it will pull off the wall if the ground settles.





99cents said:


> You apply cement to both the pipe and the fitting and after you put it together, you give it twist. You should put a sleeve over top where it comes out of the ground. That's particularly critical when they're going to pour concrete afterwards. It's good practise anyway.


It's amazing that many do not know these very critical steps. Glue both surfaces, set it in all the way, twist and hold, I was taught that as a young apprentice, yet I see so many just put a little dab on one side, little push and let go.


----------



## oliquir (Jan 13, 2011)

i also clean the pvc with acetone before putting glue


----------



## 99cents (Aug 20, 2012)

oliquir said:


> i also clean the pvc with acetone before putting glue


It's an extra step that virtually guarantees a good joint. PVC cement has the solvent built in but a two step process is the best. The acetone breaks down the shiny surface and makes it more porous.


----------



## cdslotz (Jun 10, 2008)

Cleaner first....always


----------



## John Valdes (May 17, 2007)

Signal1 said:


> It's amazing that many do not know these very critical steps. Glue both surfaces, set it in all the way, twist and hold, I was taught that as a young apprentice, yet I see so many just put a little dab on one side, little push and let go.


I know one guy that uses no glue. I don't think he would do that in this situation. But he does do it above ground and he has had success and never gets glue on his hands. 

I have never used primer/cleaner on electrical conduit. But it is a must on pressurized water lines and other pressurized liquids.
I also always use glue. I just thought it was pretty neat he does not use glue and seems to work.


----------



## dawgs (Dec 1, 2007)

John Valdes said:


> I know one guy that uses no glue. I don't think he would do that in this situation. But he does do it above ground and he has had success and never gets glue on his hands. I have never used primer/cleaner on electrical conduit. But it is a must on pressurized water lines and other pressurized liquids. I also always use glue. I just thought it was pretty neat he does not use glue and seems to work.


How does he not use glue and can shove the conduit all the way into the coupling or fitting? The glue also works as a lube to seet the conduit together.


----------



## 220/221 (Sep 25, 2007)

mike9666 said:


> Is there a trick that i missed?


I suspect improper back fill. The ground shouldn't settle much.

Another issue could be undersized pipe/fittings. It's not uncommon. 

If the pipe is just a few 1000ths off, the joint will not be solid. If you can still twist it after 10 seconds, it will never be bullet proof. A properly sized joint will set up in under 5 seconds. If it doesn't, return that ****.




> #1 do not disturb for an hour after gluing


 :laughing::laughing::laughing:

In what world? :laughing:

We glue the pipe, put it in the ground, (maybe pull wire), bury it and move on. We don't glue pipe, find something else to do for an hour then come back and put it in the ground. A good joint is completely solid in seconds. A bad joint will never be solid. 

It's all about the tight fit and a thoughtful back fill.


----------



## John Valdes (May 17, 2007)

dawgs said:


> How does he not use glue and can shove the conduit all the way into the coupling or fitting? The glue also works as a lube to seet the conduit together.


I guess we should ask him. Its Miller from long ago. He told the forum this.
But I can see it working. But I get your point.
I mean a little spit works for us guys right. In more than one circumstance. :thumbup: I wish I knew about that when I was 15!


----------



## MechanicalDVR (Dec 29, 2007)

John Valdes said:


> I guess we should ask him. Its Miller from long ago. He told the forum this.
> But I can see it working. But I get your point.
> I mean a little spit works for us guys right. In more than one circumstance. :thumbup: I wish I knew about that when I was 15!


SomeTHINGS need vaseline or similar...


----------



## 99cents (Aug 20, 2012)

I went back to back between a JB and a panel last week and didn't use any cement. There's no need. You can tell if the pipe is fully inside the TA just by looking at it. No spit, no lube, no vaseline.


----------



## MechanicalDVR (Dec 29, 2007)

99cents said:


> I went back to back between a JB and a panel last week and didn't use any cement. There's no need. You can tell if the pipe is fully inside the TA just by looking at it. No spit, no lube, no vaseline.


Size matters after 3/4"....


----------



## telsa (May 22, 2015)

1) Your backfill technique must be terrible to have that much motion.

2) In cold climates -- if the amount exposed above the frost line is significant -- a slip coupling is required.

3) Use 'hot' glue -- the super fast, super strong stuff -- or go with the two-can system: primer and agent. ( Required for plumbing )

4) If you glued up PVC in hot weather -- figure on it running low on THF -- the solvent.

http://www.ashland.com/products/tetrahydrofuran-thf-solvent

THF is manufactured by the ton -- and if you're in a hot climate -- you should have spare bottles of THF to top up the common PVC glue. As a chemical reagent it's much cheaper than the stuff in the can we use. 

( Don't use THF in the other systems. )


----------



## papaotis (Jun 8, 2013)

220/221 said:


> I suspect improper back fill. The ground shouldn't settle much.
> 
> Another issue could be undersized pipe/fittings. It's not uncommon.
> 
> ...


just read a can of cerro glue. it says good handling bond after 4 minutes, good strenght after 4 HOURS. there is another brand dont remember that says something like dont disturb for an hour


----------



## MechanicalDVR (Dec 29, 2007)

papaotis said:


> just read a can of cerro glue. it says good handling bond after 4 minutes, good strenght after 4 HOURS. there is another brand dont remember that says something like dont disturb for an hour


The one hour deal sounds like Oatey brand.


----------



## papaotis (Jun 8, 2013)

might be the same, but i was reading a cerro


----------



## dawgs (Dec 1, 2007)

John Valdes said:


> I guess we should ask him. Its Miller from long ago. He told the forum this. But I can see it working. But I get your point. I mean a little spit works for us guys right. In more than one circumstance. :thumbup: I wish I knew about that when I was 15!


 A man could dehydrate pretty quick doing a duct bank of 4".


----------



## mike9666 (Jul 28, 2015)

Not a hot climate. I think what had happened was customer didn't have eavestough installed yet, rained a ton all spilled into where the pipe was buried causing it to settle. Just thought maybe i should use an expansion joint next time.... Thanks for the input


----------



## MechanicalDVR (Dec 29, 2007)

mike9666 said:


> Not a hot climate. I think what had happened was customer didn't have eavestough installed yet, rained a ton all spilled into where the pipe was buried causing it to settle. Just thought maybe i should use an expansion joint next time.... Thanks for the input


Compact backfill under your sweep location and use an expansion joint, you'd be all squared away.


----------



## Palm (Jun 27, 2016)

A little off topic, but it's on my mind.

With the amount of flex in 1/2 and 3/4 sticks, I'm thinking about avoiding shallow couplings altogether in trenches, only using bell ends for touchy small sizes. The larger sizes are rigid enough to force kids running the pipe to brace it underneath for elevation changes. Is this a better strategy than hoping the guys tired from digging will carefully backfill everytime?


----------



## Cow (Jan 16, 2008)

Palm said:


> A little off topic, but it's on my mind.
> 
> With the amount of flex in 1/2 and 3/4 sticks, I'm thinking about avoiding shallow couplings altogether in trenches, only using bell ends for touchy small sizes. The larger sizes are rigid enough to force kids running the pipe to brace it underneath for elevation changes. Is this a better strategy than hoping the guys tired from digging will carefully backfill everytime?


For the same reasons you've mentioned, we don't use couplings in underground unless absolutely necessary, especially in small conduit sizes. The project we're on now has probably 12,000 feet so far in 3/4" and 1" sizes, I bet we've used less than 10 couplings.


----------



## MikeFL (Apr 16, 2016)

Cow said:


> For the same reasons you've mentioned, we don't use couplings in underground unless absolutely necessary, especially in small conduit sizes. The project we're on now has probably 12,000 feet so far in 3/4" and 1" sizes, I bet we've used less than 10 couplings.


Holy Cow! (pun intended)


----------



## 360max (Jun 10, 2011)

99cents said:


> I went back to back between a JB and a panel last week and* didn't use any cement*. There's no need. You can tell if the pipe is fully inside the TA just by looking at it. No spit, no lube, no vaseline.


...and yet, still a code violation


----------



## TGGT (Oct 28, 2012)

Use rigid 90's to stub up and make sure it's secured well, and only use PVC for your horizontal runs.


----------



## MechanicalDVR (Dec 29, 2007)

TGGT said:


> Use rigid 90's to stub up and make sure it's secured well, and only use PVC for your horizontal runs.


Never seen that done before, you do this on a regular basis ?


----------



## Majewski (Jan 8, 2016)

I just googled it. Found a diy forum talking about it. I kinda wanna try it now.


----------



## TGGT (Oct 28, 2012)

MechanicalDVR said:


> Never seen that done before, you do this on a regular basis ?


No. On this particular job we did. All runs switched to rigid when stubbed up from. 3/4" to 3". Just an option for the OP in case this is a common issue. I agree with other posters it probably wasn't glued correctly / back filled right.


----------



## MikeFL (Apr 16, 2016)

I've seen job specs that call for rigid u/g at the turns and I've seen a blown up POCO tranny from not following those specs.


----------



## splatz (May 23, 2015)

Besides not pulling apart, you aren't likely to burn through the rigid 90 with string.


----------



## TGGT (Oct 28, 2012)

splatz said:


> Besides not pulling apart, you aren't likely to burn through the rigid 90 with string.


One job we used fiber glass 90's. They were more like 85* and it was EXPOSED. It was ugly.


----------



## Arc'n'Spark (Jul 21, 2011)

Rigid through the slab used to be a very common spec. I still do it for exposed work and stub-ups that I know are going to sit out in the open for a while. It's easier to throw a hickey on a rigid stub and straighten it back out than it is to chip the slab out enough to cut back pvc and put a coupling or FA on it.


----------



## sparky970 (Mar 19, 2008)

MechanicalDVR said:


> Never seen that done before, you do this on a regular basis ?



This is very common for our industrial jobs, but they usually spec PVC coated rigid for buried 90's and stubbing out of the ground.


----------



## Cow (Jan 16, 2008)

MechanicalDVR said:


> Never seen that done before, you do this on a regular basis ?


All the time. There is no worry about burning 90's this way with the string. 

Here's an equipment room for a large dairy we're wiring right now. The last pic shows all the conduits covered in flowable fill to get the compaction required before concrete.


----------



## Ty the electric guy (Feb 16, 2014)

Cow said:


> All the time. There is no worry about burning 90's this way with the string.




Do your rigid 90's not need to be bonded in some way?


Sent from my iPhone using Tapatalk


----------



## Cow (Jan 16, 2008)

Ty the electric guy said:


> Do your rigid 90's not need to be bonded in some way?
> 
> 
> Sent from my iPhone using Tapatalk


As long as the metal elbows are at least 18" down in the dirt OR covered by at least 2" of concrete, then it's not required.


----------



## JRaef (Mar 23, 2009)

dawgs said:


> How does he not use glue and can shove the conduit all the way into the coupling or fitting? The glue also works as a lube to seet the conduit together.


Spit?
KY?


----------

