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Author:
Fixitangel (NC)
Very interesting. Thanks for the info, and a tip o' the hat to Jan.
I gotta ask: is the purple in purple primer a necessary chemical, or is it purely a dyeing agent so that inspectors can visually check if primer was used? That is some nasty stuff to clean after a spill. No matter how careful I am, it seems a few drops will get on something it's not supposed to.
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Author:
hj (AZ)
The "purple" is an indicator, but there are clear primers. It does soften the surfaces to give better adhesion. Regardless of Sum's testing, I will still use it, because I have seen MANY systems installed without primer that eventually failed.
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Author:
bernabeu (SC)
sorry to be the bearer of bad news, but:
the 'testing' was based on faulty INITIAL workmanship
the joints were NOT made with FULL DEPTH insertion
full depth insertion into the tapered socket is REQUIRED for the compression aspect of 'solvent welding' to be successful
therefor:
the ONLY conclusion would be that in an improperly assembled joint the primer may not be of any use
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Author:
KCRoto (MO)
If you want to clean up your joints and keep the inspector happy, get clear primer and a purple sharpie marker..
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Author:
hj (AZ)
Then try to convince him you were not trying to put one over on him, and you REALLY did do the joints properly. Also, be prepared for him to use a magnifying glass when he does any future inspections for you.
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Author:
North Carolina Plumber (NC)
We have to use purple cleaner here also. I once had an oral agreement with an inspector that I could use clear cleaner in his county if I cleaned the writing off the pipe near each glue joint. That worked well for a few years till he retired.
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Author:
needtoknow (GA)
in response to bernabeu -
His premise was to determine the strength of the actual welded joint, not the assembled parts. In the compression test it makes sense NOT to fully insert the pipe into the fitting. That way the mechanical ridge in the bottom of the hub does not get any credit in determining the force required to shear the glue joint. In fact you wouldn't know when the glue/weld failed because the pipe would already be sitting on the ridge.
So a full depth insertion would cloud the actual intent of what he was trying to show. In the compression test he could have left out the glue and/or primer entirely and probably gotten a higher force because then the failure load would then represent the force required to buckle or crush the entire assembly.
Similarly for the torsion test, his apparatus is set up to shear the adhesive layer not break the assembly pieces.
You are debating his workmanship but seem to have missed the intent of the study as was stated.
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Author:
bernabeu (SC)
If the joint is made properly
repeat if
there would not be an 'assembly layer' to break.
There would be a solvent WELDED one piece assembly.
The compression imparted by the tapered fitting is NECESSARY to solvent weld.
If not fully inserted then there can NOT BE a welded joint.
To obtain REQUIRED compressive force REQUIRES full insertion.
If not compressed then no solvent weld can exist, merely a glue joint.
As was shown: in a merely glued joint primer makes no difference.
Albeit SOME of the joints held in the twist test.
A longitudinal compression test serves no purpose.
as per:
"* The pipe is not fully seated into the fitting socket in order to allow space for it to fail during the compression test and in order for it to be weak enough to fail for the torsion test."
the only thing being tested were GLUE joints, NOT SOLVENT WELDED joints.
Jan probably got a good grade for the ineffective science project which compared the failure of one improper joint to another improper joint.
Sum's son is probably WAY SMARTER than all the chemists and engineers at the plumbing supply manufacturers - good luck waiting for them to be brutally honest with y'all.
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
bernabeu (SC)
Vic,
Thank you for the edit - much better.
Your silence on the 'content' speaks volumes.
I will bet you understand the following acronym: GIGO (no matter how well intentioned)
====
(this note is from Vic specifically intended for bernabeu) ....
whenever I feel a need to "modify" (soften) a few of your words I think of Ralph Kramden in the Honeymooners. "Sometimes .... sometimes ...!!!"
Yes, sometimes you can be a bit harsh and I have a choice at that time .... delete or soften your words. My hope is that we old timers will show total respect for those of all ages.
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Author:
needtoknow (GA)
The glue will bond with the pvc regardless of whether it is bottomed out or not. Call it glued, welded, bonded, cemented its just semantics. Otherwise how do you explain the failure numbers he reports? the strengths he recorded are over 450 lbs. for only 1/4 inch insertion. That is bonded in my book.
He created welded joints and documented strength values. He wasn't trying to pass a plumbing skills test. The amount of surface area covered will make a difference but all his test specimens match each other (as they should in this type of testing). Had he sunk the pipes in a bit further, he would have shown stronger joints. But the comparative study was between primer and no primer. I think he showed that pretty well.
As for calling the boy's work an ineffective science project, what technical data can you offer from all your experience that would allow for debate? As for debating his brain power against plumbing supply house technical experts, I venture to say they would give him credit for a great study.
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Author:
vic (CA)
"But the comparative study was between primer and no primer. I think he showed that pretty well."
Thank you very much for your words needtoknow. I agree with you.
Trying to stay out of this and being impartial and "detached" is difficult for me right now.
Vic
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Author:
packy (MA)
so now my question is, 'what is in combination glue and primer?'..
[www.amazon.com]
can't we make our own concoction?
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Author:
bernabeu (SC)
from the study itself:
Quote
The first step is pressing, and it is required to ensure contact between the two pieces being welded, maintain proper orientation of the pieces and to force intermolecular diffusion between the two pieces
The degree of insertion into the tapered fitting would GREATLY effect the compressive forces on the area to be solvent welded.
An actual properly made solvent welded joint will have NO 'line of demarcation' between the two fused together solvent WELDED pieces.
Theoretically the fitting would break just as likely as the pipe.
Unless the very concept of solvent welding is utter Torric Ka-Ka.
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
Jan (FL)
Vic, thanks so much for posting the results of my tests and allowing them to be shared with the community. I got very good feedback for the project at school and earned an A+ for the class last semester.
It has been an interesting project for me from the initial planning stage when we tried to figure out how to execute the project and I saw my dad's threads on plbg.com discussing it and getting input from everyone, to actually working on the project and compiling the results. My initial assumption was that primer would create a stronger joint. The only question was, how much stronger? It was only when the various tests showing that primed joints were actually weaker that things got really interesting.
We knew there were limitations going in, and my dad was complaining about the cost of so many PVC fittings and cements . I did consider the impact of not inserting the pipe all the way into the fitting but though the results still would be proportional. My dad told me that there was a previous discussion on it and that he would post later to explain further. I enjoyed reading all the replies and comments here.
I definitely learned a lot during this project, and my dad told me that since I have become so proficient in making PVC joints that I should help him with his next project, which is to run an underground PVC electrical conduit from the meter to an outside shed, and he told me I can decide whether to use primer or not.
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Author:
vic (CA)
You only received an A+?
I think an A+ + + + + + + plus triple extra credit
I think maybe you're ready to become the teacher of the next class on how to do studies.
Congratulations on a study SUPER WELL done!
Thank YOU for allowing us to share this with the world. Your family and friends should be VERY proud of you!
The very best to you and I'm going to mail you a personal (not business related) check for $1,000. towards your college education as we need many more people like you.
Vic
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Author:
bernabeu (SC)
Jan,
While I disagree with the application of your results I applaud your methodology and effort.
Thank you for making me engage the clutch on my retired brain.
Well done.
John S Bernabeu
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
hj (AZ)
An electrical conduit does NOT have any internal pressure and should NOT have external stress, so you could probably assemble it without any cement and it would stay together. it would just keep water out if it were underground. So, primer or no primer the conduit will be the same.
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Author:
sum (FL)
Bernabeu,
All good points.
As we initially planned the tests, one of the concerns is that the tests require the pipe not to be fully seated into the hub fully, and you are correct that this means it's not a properly made joint.
Actually we had a discussion on this very topic in an earlier thread.
[www.plbg.com]
It was one of the concerns we had. However there were some counter points as well.
We looked up the application of solvent weld PVC applications besides piping. Such as PVC sheets, PVC wedges and their solvent welding guidelines did not involve compression of the pieces together. Yes some recommended "clamping" together to make it "better" but nothing to infer that compression is required to make a true solvent weld joints.
We also looked at a PVC repair coupling, which you can slide on to a pipe FULLY. It does not have a tapered socket leading to a smaller "middle". Is a repair coupling never going to attain a true solvent welded joint then? There are plenty of other PVC tubing products (not pipes) that have no tapered sockets that the manufacturers sell PVC cement to create a solvent welded bond.
So our conclusion was to not insert the pipe all the way in because our rudimentary home made test contraption would work.
There is no question that if you bottom out the pipes into the sockets, it will create a stronger joint. We felt that not inserting fully, will still yield the same RELATIVE results between joints that are primed versus unprimed. Reality is I have seen many professional plumber made PVC joints that are not full depth insertions, especially in repair situations. You guys are the "TOP GUNs" of the plumbing world with much higher standards, in the field however, as a home owner and part time RE investor, I see plenty of sloppy work.
Your comment "in a merely glued joint primer makes no difference." that's not entirely correct either. The joints that were primed seem to be considerably weaker, in the initial stages, and grew stronger as time passed. After about 24 hours, they are about 50/50.
So the question that remains to be answered is, does a joint really need to be fully inserted to achieve solvent welding? Are all those people out there jointing PVC sheets, wedges and shapes all delusional thinking they were solvent welding when they just "glued"? Is it even possible to create a solvent welded joint with a repair coupling? If not, why even make one?
Perhaps we can try and answer that. If we can figure out a way to create fully inserted joints and test the primed and unprimed versions. The only problem is, as was discussed previously, how do we device the tests if the "ridge" is in the way? We don't have the resources of Myth Busters. But perhaps we can think of something, spring break is coming up right Jan?
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Author:
bernabeu (SC)
Quote
Is it even possible to create a solvent welded joint with a repair coupling?
In my purely personal opinion NO, it is NOT possible.
As to why they are made: Because there is money to be made.
They are NOT 'code approved' products.
However,
In a pinch, on drainage (non pressure), I have been guilty of using product. NEVER on a concealed pressurized line.
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
vic (CA)
"So the question that remains to be answered is, does a joint really need to be fully inserted to achieve solvent welding? Are all those people out there jointing PVC sheets, wedges and shapes all delusional thinking they were solvent welding when they just 'glued'? Is it even possible to create a solvent welded joint with a repair coupling? If not, why even make one?"
Awesome questions!
I think we need a scientist to do more studies and share those test results with us.
Hey wait a minute .... I think know a brilliant sophomore that is capable of answering those questions for us ..... if he had the time and the money.
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Author:
KCRoto (MO)
I can see a guest appearance on Mythbusters.
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Author:
Stuff (PA)
I think that this was a good start for discussion purposes but does not have a lot to do with plumbing. CPVC/PVC pipiping installed for water supply and DWV is not structrual other than supporting the weight of pipes and the water it contains. Pipe is tested and rated for burst strength. That should be the next logical study to test primer.
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Author:
sum (FL)
While I think that burst strength would have been nice to be included into the tests, we didn't have a lab or the resources of Mythbusters at our disposal. I disagree that a burst test is all that matters.
At the end of the day, solvent welding is welding two pieces of similar plastics together into a single fused piece. It should withstand pressure whatever which ways. Whether it's from internal water pressure, external pressure, compression, tension, shear, torsion etc...
Bear in mind the topic being studied is whether a primer "enhances" the strength of the PVC joint, not whether the joints created in these tests are "properly made" or "good for plumbing".
If burst strength is all that counts, and the other tests do not, then one has to accept the likely conclusion that a primer will only enhance solvent welded joints subjected to water pressure, but wouldn't if these same solvent welded joints are subjected to other pressures or forces, and that to me doesn't make sense. You have two supposedly solvent welded joints, one made with primer, one made without, which one is stronger?
DWV systems are not subjected to water pressure...except I guess when it clogs or during your pressure head tests during inspection, the only plastic pipes that would be subjected to water pressure would be PVC irrigation systems and CPVC supply pipes. You have construction workers stepping on newly laid drain lines and irrigation lines, pest control people, plumbers, inspectors, roofers, AC techs stepping on CPVC lines and condensate lines in attic all the time, and pipe joints being pulled and tugged as they are being strapped down to studs, and continue to do as walls and foundation settle and wood expand and contracts. Lawn mowers shaking down sprinkler lines 3 inches below, a plumber twists a joint a minute later after noticing it's not entirely vertical...so on the practical end, I bet (I am not a plumber so no real data to fall back on but just a hunch here) there are more joint failures due to mechanical forces then due to excessive water pressure. For these reasons I believe the tests used in these experiments are more useful, if not at least as useful as a burst test, for plumbing purposes.
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Author:
Jan (FL)
I received a very nice thank you card from Vic complimenting my work and the project, including a $1000 gift to be used to further my education! Vic, thank you for your generosity, thank you for this act of kindness. I hope one day I will be able to provide contribution and encouragement for others as you have done for me.
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Author:
Jan (FL)
[www.oatey.com]
Thank you everyone for your feedback. After reviewing the above diagram, there is a question of whether the project I did was based on joints made at the "entrance" portion of the fitting instead of the full depth of the fitting, where according to the picture, solvent welding happened. While I can provide several arguments supporting the validity of our test, I do see that I might need to think of a way to test the strength of a joint where it is fully inserted. I don't have any idea how to do that yet or what equipment is needed, but I'll consult with my dad to see if we can think of something. I will post again when we have a better idea.
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Author:
Lworkman (CA)
In addition the the other comments about some faults with this test it should be noted that PVC and CPVC joints will NOT reach full cure in 24 hours. The solvents in the cement and solvent have NOT completely flash or evaporated especially in internal portion of the joint. Most solvent manufacturers will state 48 hrs for a 75-80% cure.
In addition the use of a primer is an indicator of the installers workmanship, just as the use of a primer before painting a bare metal car body is. Would you want the painter to just apply the paint and not prime first?
Pipe and fittings on a job site have an accumulation of dust, dirt and grime from transportation, storage, and handling. The use of primer assists in getting the surfaces close to the laboratory conditions of Mr. Lin's study! In my over four decades of evaluating field failures of PVC Joints, the joints that had been primed consistently were significantly fewer and of higher quality.
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Author:
Lworkman (CA)
In addition the the other comments about some faults with this test it should be noted that PVC and CPVC joints will NOT reach full cure in 24 hours. The solvents in the cement and solvent have NOT completely flash or evaporated especially in internal portion of the joint. Most solvent manufacturers will state 48 hrs for a 75-80% cure.
In addition the use of a primer is an indicator of the installers workmanship, just as the use of a primer before painting a bare metal car body. Would you want the painter to just apply the paint and not prime first?
Pipe and fittings on a job site have an accumulation of dust, dirt and grime from transportation, storage, and handling. The use of primer assists in getting the surfaces close to the laboratory conditions of Mr. Lin's study! In my over four decades of evaluating field failures of PVC Joints, the joints that had been primed consistently were significantly fewer and of higher quality.
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Author:
Pop Alexandra (Non-US)
That's amazing. I also received some materials from [revetementagro.com] back in the day. Some companies know how to treat their clients.
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