Joining Method Solvent Weld

Solvent welding, also known as solvent cementing or solvent bonding, is the process of joining pipes made of thermoplastic resins by applying a solvent capable of softening the surfaces to be joined, and pressing the softened surfaces together. The pipe and fittings are bonded together by means of chemical fusion. Solvents contained in primer and cement soften and dissolve the surfaces to be joined. Once the pipe and fitting are assembled, a chemical weld occurs. This weld strengthens over time as the solvents evaporate.

Solvent cement joining always involves a pipe or tube end and fitting socket or pipe bell. The inside of the socket is slightly tapered, from a diameter slightly larger than the pipe OD at the entry, to a dimension at the base of the socket that is a few thousandths of an inch smaller than the pipe OD. Thus, the pipe-to-socket match-up results in an interference fit more-or-less midway in the socket. Solvent cement is applied to the outside of the pipe end and the inside of the socket. The pipe is then pushed into the socket until it bottoms. Some codes require a primer to be applied before the solvent cement.

This technique is often incorrectly described as “gluing” the pipe together. This is not accurate because gluing is an adhesion process. That is, the two parts joined remain two individual parts held together by the glue – a different material. For example, gluing wood pieces together does not make one piece of wood. Solvent welding of plastic pipe is a cohesion process similar to welding of metal. Once the weld is complete, the two pipes become one. The solvent is used simply to “melt” the pipe. Once the pipe has solidified, the solvent evaporates, leaving only the pipe. 

ABS, CPVC, and PVC plastic pipes are primarily joined by solvent cementing, though mechanical joints are also available. PE and PEX pipe cannot be joined with solvent cements. When joining pipe and fittings with solvent cement, the pipe ends must be cut square, beveled and deburred. Appropriate primer and solvent must be used per manufacturer’s application instructions, and the pipe must be rotated 1/4 turn as it is inserted and bottomed in the socket.

Relevant Materials And Systems

Purple Non-Potable Water Pipe

Manufactures and Suppliers Participating in OPUS