Frequently Asked Questions - Weld-On

Frequently Asked Questions

Solvent welding is a chemical process that uses a primer, or the cement itself, to soften the surface of plastic pipe and fittings in order to weld, or fuse them together. This requires a tight, or interference fit. The solids contained in the solvent cement will then fill the gap between the pipe and fitting. Glue such as PVC glue, on the other hand, is only a bonding cement and will not work with an interference fit.

Primers pre-soften the surface of the pipe and fitting before the solvent cement is applied so that maximum fusion can take place.

To remove grease, dirt, and foreign matter from the surface of the pipe and fitting prior to application of the primer and cement.

The Set Time is the amount of time the joint is to be left undisturbed before handling. The Cure Time is the amount of time it takes the joint to be completely set and ready for pressure to be applied.

VOC stands for Volatile Organic Compounds which are emissions from materials. Low VOC products contribute to cleaner air. The requirements for “Low VOC” have been established by SCAQMD Rule 1168/316A.

This phenomenon is caused by moisture being drawn into the cement (only at the surface) during the first part of the curing process and is not harmful to joint strength.

Low VOC solvent cements and primers are currently required in California, Maryland, New Jersey and Connecticut. Requirements are also under consideration in several other states, including New York, Rhode Island, and Maine. Even where not required, Low VOC products are a good idea because they contribute to cleaner air and a healthier environment.

Weld-On’s Low VOC solvent cements and primers provide the same performance, have the same installation properties, but are better for the environment and more user-friendly than non-Low VOC products.

Yes. CPVC solvent cement technically will work on PVC piping. However, we recommend that the correct Weld-On primer and PVC solvent cement for the particular application should be used. Please note that PVC solvent cement, because of temperature limitations, is not recommended for CPVC piping.

No. The Weld-On primer must be wet and fluid. The purpose of the primer is to soften the joining surfaces of the pipe and fitting allowing proper penetration and dissolution of joining surfaces prior to Weld-On solvent cement application. This step is specifically recommended for large diameters, PVC Schedule 80, CPVC piping and cold weather installations.

No. For 4-inch and larger diameter piping, we recommend the use of 4-inch swab to apply our primers and solvent cements. A can dauber is appropriate for use on pipe diameters that are approximately twice the size of the dauber diameter.

No. However, we recommend the use of primer on all PVC piping systems. Some Weld-On PVC solvent cements for irrigation piping can be used without primer on non-pressure systems if local codes permit.

Identify the parameters of the particular application:

  • Pipe material – PVC, CPVC, ABS
  • Schedule or SDR of piping – Sch.40, Sch.80, SDR21, etc.
  • Pipe diameter
  • Working pressure of piping system
  • Ambient temperature at the time of installation
  • Temperature of media conveyance within the piping system
  • Type of media being conveyed within the piping system – water, specific chemicals, etc.
  • Other variables which may affect application and/or piping syste

Consult the Weld-On Selection Guide and Product Guide for more information or contact your local Weld-On sales representatives for recommendation. Please call 1-800-888-8312 for your nearest Weld-On sales representative office. If further technical assistance is required, contact our Technical Service Hotline at 1-877-477-8327.

Weld-On primers, PVC and ABS solvent cements: 3 years shelf life
Weld-On CPVC solvent cements: 2 years shelf life

All Weld-On primers and solvent cements have expiration dates imprinted on the outside of the case boxes and the manufactured date imprinted on the bottom of each can. The shelf life is also stated in the product bulletin of each Weld-On product.

Please refer to Product Literature and/or browse through our website for more product details.

In response to questions concerning solvent cement joint strength vs. PVC pipe pressures and surges; the shear strength of a well-made/fully-cured solvent cemented joint is always stronger than the individual pipe or fitting itself.  This is regardless of the pipe diameter, schedule of wall thickness, PVC compound formulation, or system pressure/temperature.