# Connecting rigid pvc conduit to flex pvc conduit



## MechanicalDVR (Dec 29, 2007)

Most times you see a male adapter on the pvc and a male connector on the flex and a rigid coupling in the middle which looks super hack but passes. I would use a flex connector (with a male end) and a glue on female adapter and it looks decent and passes. 

I have been told gluing non metallic flex into a pvc coupling is within code but never done it myself.


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## Bird dog (Oct 27, 2015)

I tend to agree with MechDVR to use a female adapter (FA). The rigid coupling wouldn't be bonded & I'm not sure the glue joint between the flex and the PVC would withstand the longterm flexing.


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## splatz (May 23, 2015)

http://www.homedepot.com/p/3-4-in-P...x-Female-NPT-Thread-Adapter-835-007/202983479


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## Roger123 (Sep 23, 2007)

MechanicalDVR said:


> I have been told gluing non metallic flex into a pvc coupling is within code but never done it myself.


Been tempted to do that a number of times, but think that is a listing violation.


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## telsa (May 22, 2015)

Splatz posted the correct solution.

And it's cheap and very widely available. :thumbsup:


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## OldMasterTech (Mar 12, 2014)

Glued 2" rigid PVC to 2" flex PVC with a coupling last year. I remember thinking I did not like the fit on the flex and it took the glue a long time to set. However the work passed.


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## Southeast Power (Jan 18, 2009)

OldMasterTech said:


> Glued 2" rigid PVC to 2" flex PVC with a coupling last year. I remember thinking I did not like the fit on the flex and it took the glue a long time to set. However the work passed.


Ive done this plenty of times and we have very strict building departments in some jurisdictions here.


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## Southeast Power (Jan 18, 2009)

MechanicalDVR said:


> Most times you see a male adapter on the pvc and a male connector on the flex and a rigid coupling in the middle which looks super hack but passes. I would use a flex connector (with a male end) and a glue on female adapter and it looks decent and passes.
> 
> I have been told gluing non metallic flex into a pvc coupling is within code but never done it myself.


This is what we normally do but, I would glue carflex into a PVC coupling.


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## Going_Commando (Oct 1, 2011)

I've pulled apart joints by hand where carflex was glued into a pvc coupling, so i wont do it. Female adapter on the pvc and a carflex connector is my preference


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## MechanicalDVR (Dec 29, 2007)

Roger123 said:


> Been tempted to do that a number of times, but think that is a listing violation.


I've seen it fly but I think it looks cheap and unreliable.


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## Roger123 (Sep 23, 2007)

"Copied from a poster at Holt Web Site" 


From the Carlon website: 

Can you glue Carflex directly into Carlon PVC fittings?
Sorry, but fittings are not allowed to be glued or solvent-cemented to Carflex
directly. Only a mechanical connection is allowed and you can only use
Liquidtight Flexible Nonmetallic Type B fittings with our Carflex.


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## MechanicalDVR (Dec 29, 2007)

Roger123 said:


> "Copied from a poster at Holt Web Site"
> 
> 
> From the Carlon website:
> ...


Great to know but I don't think all the inspectors realize it. I've seen it done many times. I've never cared for the way it felt fragile to me.


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## splatz (May 23, 2015)

A lot of times you can glue plastic and it feels real solid when it dries, but six months later it's falling apart. For a lasting bond you have to have a glue that's right for both plastics, the surfaces, the fit, etc.


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## telsa (May 22, 2015)

splatz said:


> A lot of times you can glue plastic and it feels real solid when it dries, but six months later it's falling apart. For a lasting bond you have to have a glue that's right for both plastics, the surfaces, the fit, etc.


Preach it.

BTW, PVC is not so much as glued as WELDED.

The solvent we use is intended to dissolve a thin layer of PVC -- and then the two surfaces blend into each other.

The primary solvent used -- the ones electricians use -- is THF.

Tetra Hydro Furan.

This stuff can be purchased for FAR LESS from any chemical supply firm... by the quart or gallon... or drum. The chemical industry makes it by the mega-ton.

The rest of the goop we use is nothing much but stabilizers designed to keep the THF in the can, make it pasty while it's applied. They are actually not the active ingredient.

Pure THF is as runny as water.


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## Roger123 (Sep 23, 2007)

Talking about gluing PVC, just finished a job where the home owner had his own trenching done, about 200ft., installed PVC Conduit in 10ft sections and glued after he installed the wire in the conduit sections. 

I was a bit nervous about the glue possibly damaging the wire. 

So, has anybody actually seen or even heard of the glue we use damaging wire when the conduit is glued together after the wire is pulled?

In this case, no damaged was detected, but I only megged the wires.


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## B-Nabs (Jun 4, 2014)

Roger123 said:


> Talking about gluing PVC, just finished a job where the home owner had his own trenching done, about 200ft., installed PVC Conduit in 10ft sections and glued after he installed the wire in the conduit sections.
> 
> I was a bit nervous about the glue possibly damaging the wire.
> 
> ...


My other concern would be the likelihood that those wires will never want to move again, negating the benefit of using pipe. Might as well have run cable at that point.


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## 99cents (Aug 20, 2012)

B-Nabs said:


> My other concern would be the likelihood that those wires will never want to move again, negating the benefit of using pipe. Might as well have run cable at that point.


The cement definitely gets inside the pipe. I ONCE made the mistake of pulling Cat 5 through PVC conduit as I put the pipe together. I could see the danger of the solvent cement melting the insulation on conductors.


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## telsa (May 22, 2015)

Roger123 said:


> Talking about gluing PVC, just finished a job where the home owner had his own trenching done, about 200ft., installed PVC Conduit in 10ft sections and glued after he installed the wire in the conduit sections.
> 
> I was a bit nervous about the glue possibly damaging the wire.
> 
> ...


The actual insullator // dielectric around the copper of THWN is PVC. This is the same stuff as the PVC pipe we use all the time. The difference is that THWN PVC is loaded with additional goop to keep it super flexible -- to never really harden up.

The exterior coating is nylon:

Nylon 66 is synthesised by polycondensation of hexamethylenediamine and adipic acid. Equivalent amounts of hexamethylenediamine and adipic acid are combined with water in a reactor. This is crystallized to make nylon salt, which has precisely stoichiometric equivalents. The nylon salt goes into a reaction vessel where polymerization process takes place either in batches or continuously.
n HOOC-(CH2)4-COOH + n H2N-(CH2)6-NH2 → [-OC-( CH2)4-CO-NH-(CH2)6-NH-]n + 2n H2O
Removing water drives the reaction toward polymerization through the formation of amide bonds from the acid and amine functions. Thus molten nylon 66 is formed. It can either be extruded and granulated at this point or directly spun into fibres by extrusion through a spinneret (a small metal plate with fine holes) and cooling to form filaments.

&&&&&&

Rather than troll the Internet, conduct your own experiment. Take a short length of THWN-2 and try and glue it to any random hunk of scrap PVC. 

If you remove the nylon sheath, it's a certainty that PVC will weld with PVC. :thumbsup:

I can assure you that because THF melts PVC, dang near ANYTHING will fuse into it.


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