[Abuc]

This is probably old news to most of you but I thought it was worth posting. Came across it a while ago when I was researching cure times. Looks like primer is more likely to weaken a joint rather than strengthen it.

https://www.plumbingsupply.com/the-great-pvc-primer-debate.html

 

[Ghostmaker]

PVC


705.11.2 Solvent cementing. Joint surfaces shall be clean and free from moisture. A primer that conforms to ASTM F 656 shall be applied. Solvent cement conforming to ASTM D 2564, CSA B 137.3, CSA B 181.2 or CSA B 182.1 shall be applied to all joint surfaces. The joint shall be made while the cement is wet and shall be in accordance with ASTM D 2855. Solvent cement joints shall be permitted above or below ground.
Exception: A primer is not required where both of the following conditions apply:
1. The solvent cement used is third-party certified as conforming to ASTM D 2564.
2. The solvent cement is used only for joining PVC drain, waste and vent pipe and fittings in nonpressure applications in sizes up to and including 4 inches (102 mm) in diameter.

CPVC

605.15.2 Solvent cementing. Joint surfaces shall be clean and free from moisture. Joints shall be made in accordance with the pipe manufacturer's installation instructions. Where such instructions require that a primer be used, the primer shall be applied to the joint surfaces and a solvent cement orange in color and conforming to ASTM F 493 shall be applied to the joint surfaces. Where such instructions allow for a one-step solvent cement, yellow in color and conforming to ASTM F 493, to be used, the joint surfaces shall not require application of a primer before the solvent cement is applied. The joint shall be made while the cement is wet and in accordance with ASTM D 2846 or ASTM F 493. Solvent cemented joints shall be permitted above or below ground.



Most professionals use one step glue on CPVC


PVC Water


605.22.3 Solvent cementing. Joint surfaces shall be clean and free from moisture. A primer that conforms to ASTM F 656 shall be applied. Solvent cement conforming to ASTM D 2564 or CSA B 137.3 shall be applied to all joint surfaces. The joint shall be made while the cement is wet and shall be in accordance with ASTM D 2855. Solvent-cement joints shall be permitted above or below ground.



This requires priming. Also, not to be used inside a building as water distribution piping. Only approved for water service. (from source to building)

 

[Oso954]

I wouldn't accept his test results as proof of anything. He pretty much accepts that when he lists manual assembly length as an inconsistency.

With a joint of 1/4 inch (plus or minus) the results have no real comparison to a full insertion joint.

Most of his joint failures were between 1600-2000 newtons. That's 360-450 pounds force.

As a high school science project, give him a good grade for the "experiment" and write up, but I wouldn't draw any conclusions from it.

 

[SPS-1]

Looks like primer is more likely to weaken a joint rather than strengthen it.

Only if you measure the strength while the plastic is still soft. The purpose of the primer is to soften the substrate to ensure complete fusion.

Besides, I am not buying into his numbers. If you look at compressive strength after 24 hours, primed and unprimed is identical down to the 0.1 N. NASA could not produce results that identical if they tried.

The variable in his tests is time. How about temperature ? How about pipe cleanliness ? How about other variables that I can't even contemplate, not being an expert on solvent welding.


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[ront02769]

Regardless of the effect of the primer on pipe strength, where I am if the inspector doesn’t see the tell tale purple primer on a joint, you cut it out and do it over. Ron

 

[bruceb3]

I've replaced too many failed unprimered joints to buy into that. A properly primed and glued joint is stronger than the pipe. Try to get a primed and glued joint apart after 10 minutes and tell me what you think.