How to Solvent Weld a PVC Pipe System?
PVC pressure pipes and fittings are designed for an interference fit. Although PVCu solvent cement has good gap filling properties no attempt should be made to increase the clearance between pipes and fittings by excessive abrading. PVCu solvent cement welding offers a simple and quick means of constructing high integrity leak free joints. Correctly made joints are stronger than either pipe or fitting. The solvent cement operates by chemically softening the outside of the pipe and the inside of the fitting. Joint integrity is greatly reduced if these surfaces are not absolutely clean and properly prepared. The procedure detailed below must be followed.
Please note under no circumstances should a sealing paste be used which could be harmful to PVCu products.
|1.||The pipe must be cut clean and square. A plastic pipe saw or suitable wheel cutter may be used.|
|2.||File a chamfer, approximately 3mm x 45°. This prevents the solvent cement layer being scraped from the surface of the fitting when the joint is assembled.|
|3.||Mark the pipe a known distance from the end and clear of the area to be abraded. This should be used to check that the pipe is all the way into the socket after assembly.|
|4.||Thoroughly abrade the end of the pipe over a length equal to the depth of the fitting socket, using clean coarse emery cloth.|
|5.||Thoroughly abrade the socket of the fitting.|
|6.||Clean thoroughly the abraded surfaces of pipe and fittings. Use a clean, lint free cloth or paper towel, moistened with MEK cleaner.|
|7.||Remove the lid from the PVCu solvent cement. Do not stir it.|
|8.||Using a clean brush, approximately half as wide as the pipe to be jointed, apply cement to the pipe and fitting using longitudinal strokes. The abraded areas should be completely covered with cement. The amount required will vary with pipe diameter and fit between pipe and fitting but should be such in all cases that the cement is still liquid to allow surfaces to slide when the pipes and fittings are assembled. It is important to apply cement quickly, to enable assembly without excessive force being required.|
|9.||Immediately after application of cement, push the pipe fully home into the fitting. Do not twist. Hold the pipe and the fitting for times varying from a few seconds on sizes 3⁄8" or 16mm to 1 minute on sizes 8" or 225mm and above. Application of the correct amount of cement will result in a neat bead of cement at the edge of the fitting and at the edge of the pipe. Excessive deposits of solvent cement inside the fittings must be avoided as these can weaken the wall, particularly on small sizes. When working under cold conditions, make sure the joints are free from frost and moisture and allow extra curing time to compensate for the lower temperature.|
|10.||Wipe off excess cement from the outside of the joint.|
|11.||Replace lids on tins.|
|12.||Clean brush in MEK cleaner.|
After 24 hours under normal conditions the cement within the joint will have dried enough to be able to withstand the rated pressure of the PVC pipe system. Please note that all drying times in a pipe system only start on the completion of the last joint. After 24 hours the pipe system can be fully pressure tested. The test pressure should be equal to 1½ times the rated pressure of the lowest rated fitting or pipe within the system.
Please note that during the jointing procedure both solvent cements and cleaners produce vapours (fumes), therefore, we recommend that the jointing procedure should be undertaken in a well-ventilated area. We also recommend ventilation within the pipe system during assembly, to disperse any potentially harmful vapours.