Common errors made when cementing plastic pipe systems

Common errors made when cementing plastic pipe systems

ABS, CPVC and PVC pipes and fittings are generally connected to each other using a solvent weld process. After cleaning the pipe and fitting of any grease or dirt, a thin film of solvent cement is painted onto both surfaces and they are pushed together in one swift movement. The solvent cement melts a thin layer of plastic on the pipe and fitting and as the solvent evaporates, these layers fuse together to form a strong seal. This would appear to be a straight forward process. Like many such processes however, there are a few do’s and don’ts that need to be followed;

·         Don’t paint the solvent cement on to the pipe first. The socket should be coated first and then the pipe. This is because the socket can be put down on a surface whilst the pipe is painted. If the pipe were painted first, it is difficult to put it down anywhere without getting grit and dirt on the cement.

·         Don’t let solvent cement or cleaner run into a valve. If at all possible unscrew the unions, or remove the flanges from the valve, glue into position and then, once the cement has dried,, reassemble the valve. Care must be taken to ensure the union nuts or flange rings are on the pipe before cementing the fitting. If the valve must remain assembled, apply the cleaner / cement to one side of the valve and sit it vertically with the cemented socket facing downward whilst you apply cement to the pipe. Push the valve downwards onto the pipe and leave to set in this position. If it is suspected that cement may have entered the valve body, turn the handle a few times to ensure the mechanism remains free. In the case of an abs valve, this must be done very quickly as the setting rate for abs is very much faster than pvc pipe.

·         Don’t twist or turn the PlasticPipe Fittings  together as they are assembled. The error is often made by inexperienced workers, who believe that it will ensure the cement is spread throughout and give a better join. What in fact happens, especially with ABS pipe and fittings (as the y set much quicker) is that the moment the two surfaces come in to contact with each other, the solvents begin to melt the plastic surfaces and they begin to fuse together. Twisting the pipe / fitting tears the newly formed, fused layer and prevents it from forming correctly. This will result in a leaking joint.

Part two of this document includes additional do / don’t tips for pvc,abs and cpvc pipe and fittings.