PVC question

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olly

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Location
Berthoud, Colorado
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Master Electrician
Correct me if I'm wrong please. It is legal to run PVC through a garage and crawlspace as long as the area is not any type of air plenum.

I have to get an 1 1/4 or 1 1/2 through there and it seems like PVC would be easier and cheaper. Any thoughts?

This will be exposed on the drywall, would SCH40 work or would I need SCH80?

Thanks for your advice.
 
Yes, no restriction on it from an NEC standpoint, just watch your securing and supporting intervals. Schedule 40 would be fine in my area but your local AHJ may see it differently. We don't use much 80 in my area, hardly ever actually.
 
olly said:
Correct me if I'm wrong please. It is legal to run PVC through a garage and crawlspace as long as the area is not any type of air plenum.

I have to get an 1 1/4 or 1 1/2 through there and it seems like PVC would be easier and cheaper. Any thoughts?

This will be exposed on the drywall, would SCH40 work or would I need SCH80?

Thanks for your advice.
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sch. 40 is where you would use emt
sch. 80 is where you would use grc.

you'll have to strap more to maintain a clean installation,
as pvc gets pretty squiggly.

i would suggest purple primer as well, as it'll let the
solvent weld be much stronger, and prevent stuff from
pulling apart with expansion and contraction later on.
 
You will have to fire stop it at the wall between the garage and the crawl space.

Now after I typed that I read what it said. Under the house crawl space or attic space?
 
pvc primer can actually make for a weaker joint ;)
unless code requires it, skip primer, if need be do a quik wipe with acetone, then use a low-moderate speed cement.
 
FionaZuppa said:
pvc primer can actually make for a weaker joint ;)
unless code requires it, skip primer, if need be do a quik wipe with acetone, then use a low-moderate speed cement.
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That's the first time I've heard of this. I use clear primer all the time on PVC connections to assure a better joint. I'm hesitant to doubt that you are correct without doing some more research but doesn't acetone also soften the PVC or have some adverse affect ?
 
electrofelon said:
Do you have a source to back up that statement, or are you being facetious?
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there a ton of tests you can find online
https://www.plumbingsupply.com/the-great-pvc-primer-debate.html
https://www.plbg.com/forum/read.php?1,504728


using primer has to be done just right to make the joint better. from the data i see, most folks dont use primer correctly and probably have weaker joints.

infinity said:
Standard PVC primer is 30-60% acetone (guess that the mixture chemical ratio is proprietary so they don't tell you the actual makeup). Not sure if 100% acetone would have a detrimental effect on the PVC conduit.

http://www.oatey.com/products/plast...rs/hercules-primers-cleaners/pvc-primer-clear
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there is no issue. you just use a rag lightly dampened with acetone, wipe the mating surfaces clean, then cement them.

and btw, there's a big diff between "primer" and "cleaner"

some locales have codes that require colorful primer, for what reasons i am not sure.
 
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I dont have time to read through those links right now, but I will say that in my experience and from some destructive tests, primered joints are stronger. I do agree that following the instructions is important. I admit I used primer inproperly for years until one day I read the can :angel:
 
FionaZuppa said:
there a ton of tests you can find online
https://www.plumbingsupply.com/the-great-pvc-primer-debate.html
https://www.plbg.com/forum/read.php?1,504728


using primer has to be done just right to make the joint better. from the data i see, most folks dont use primer correctly and probably have weaker joints.


there is no issue. you just use a rag lightly dampened with acetone, wipe the mating surfaces clean, then cement them.

and btw, there's a big diff between "primer" and "cleaner"

some locales have codes that require colorful primer, for what reasons i am not sure.
Click to expand...

Good links.

If you are to take notice, PVC cement for plumbing and PVC cement for electrical conduit are labeled different. The cement for electrical conduit has no primer step in the instructions. Plumbing cement does.

We went from having to use primer, the inspectors would look for the purple, to being prohibited from using it. Any PVC conduit cement will not have primer, and it must be used according to instructions.

Why the difference?

As the links indicate, the use of primer makes the joints weaker in all tests. So why do they still use it for plumbing? Because the primer, by virtue of softening the joints, makes them waterproof at pressure. The primer is to mitigate leaks, NOT to make a strong joint.
 
electrofelon said:
I dont have time to read through those links right now, but I will say that in my experience and from some destructive tests, primered joints are stronger. I do agree that following the instructions is important. I admit I used primer inproperly for years until one day I read the can :angel:
Click to expand...

My personal tests backed up the data in the links. Primer makes the joints softer.

A clean, unprimered joint is the strongest, but more prone to leaks.
 
electrofelon said:
I admit I used primer inproperly for years until one day I read the can :angel:
Click to expand...

I was going to read the can but decided to wait for the movie.:lol:

Actaully it's a good idea to know as much about PVC and the glue and primer as possible. Under certain conditions that stuff can be dangerous.

Working around clorine (pool house) is a good example.
 
K8MHZ said:
For the strongest PVC joints not required to be leak proof, a clean, dry surface will provide the best host for the cement. IPA is the best cleaner. Acetone is a no-no. You don't want to clean the surfaces with anything that will dissolve the PVC.
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a rag lightly damp with acetone will not dissolve the PVC.
the main goal of a quick wipe is to remove the finished product glaze (and dirt). this is all that is really needed.
another big thing is cure times for cements. slow curing cements will make for a stronger joint.

but, in context, i am not sure how strong a joint needs to be for gray UL PVC. if its in context of "needs to be super-duty strong" then the use of cleaners/primers must be in the conversation, but i am willing to bet i can create just as strong joint w/o use of a primer. proper use of primer when you get into ~6" pipe is not so ez to do.
 
FionaZuppa said:
a rag lightly damp with acetone will not dissolve the PVC.
the main goal of a quick wipe is to remove the finished product glaze (and dirt). this is all that is really needed.
another big thing is cure times for cements. slow curing cements will make for a stronger joint.

but, in context, i am not sure how strong a joint needs to be for gray UL PVC. if its in context of "needs to be super-duty strong" then the use of cleaners/primers must be in the conversation, but i am willing to bet i can create just as strong joint w/o use of a primer. proper use of primer when you get into ~6" pipe is not so ez to do.
Click to expand...

Acetone most certainly will dissolve some of the PVC. Primer only has about 40% acetone in it.

I have done this. If you want to know how strong a non primered joint is, make one and try to pry it apart after about 15 minutes. Even after only 5, it's all but impossible.

Edit to add: As an apprentice one day on a job, this argument came up so to put an end to it, we did a bunch of experiments. Anyone who doesn't agree with our results can feel free to disprove them by doing such an experiment. It takes about 45 minutes, and uses up about 2 bucks worth of material.
 
K8MHZ said:
Acetone most certainly will dissolve some of the PVC. Primer only has about 40% acetone in it.

I have done this. If you want to know how strong a non primered joint is, make one and try to pry it apart after about 15 minutes. Even after only 5, it's all but impossible.

Edit to add: As an apprentice one day on a job, this argument came up so to put an end to it, we did a bunch of experiments. Anyone who doesn't agree with our results can feel free to disprove them by doing such an experiment. It takes about 45 minutes, and uses up about 2 bucks worth of material.
Click to expand...

a dampened rag, not a drench from a swab, not a soaking rag, big diffs. you will not dissolve the PVC using a dampened rag. a small can of acetone, some clean rags, quik wipe to clean and break the glaze, no primer, proper cement and fitment, solid/strong joint.

not sure what you mean by "after 5, its all but impossible". are you talking about pulling it apart by hand? if so that has no place in this strength debate, you need to apply force by mechanical means to know how strong the joint really is.
 
FionaZuppa said:
a dampened rag, not a drench from a swab, not a soaking rag, big diffs. you will not dissolve the PVC using a dampened rag. a small can of acetone, some clean rags, quik wipe to clean and break the glaze, no primer, proper cement and fitment, solid/strong joint.

not sure what you mean by "after 5, its all but impossible". are you talking about pulling it apart by hand? if so that has no place in this strength debate, you need to apply force by mechanical means to know how strong the joint really is.
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No, not by hand. We used hammers and chisels once we realized just prying on the joint with a screwdriver wouldn't get it. For all practical purposes, the two pieces had become one.
 
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