The Way Of Splicing PVC Waterstops
We sometimes have problems with water leakage through construction joints containing polyvinyl-chloride (PVC) waterstops. We believe the leaks are occurring at splices in the waterstop. Is there a good reference on how to splice PVC waterstops so they won't leak?
In July 1995, the U.S. Army Corps of Engineers issued a revised Section 03250 (Expansion Joints, Contraction Joints, and Waterstops) of their Guide Specification for Military Construction. Here's what the specification says about splices in section 3.2.3. "Splices shall be made by certified trained personnel using approved equipment and procedures." For nonmetallic waterstops, "fittings shall be shop-made using a machine specifically designed to mechanically weld the waterstop. A miter guide, proper fixturing (profile dependent), and portable power saw shall be used to miter cut the ends to be joined to ensure good alignment and contact between joined surfaces. The splicing of straight lengths shall be done by squaring the ends to be joined. Continuity of the characteristic features of the cross section of the waterstop (ribs, tabular center axis, protrusions, etc.) shall be maintained across the splice." For polyvinyl-chloride waterstops, "splices shall be made by heat sealing the adjacent waterstop edges together using a thermoplastic splicing iron utilizing a nonstick surface specifically designed for waterstop welding. The correct temperature shall be used to sufficiently melt without charring the plastic. The spliced area, when cooled, shall show no signs of separation, holes, or other imperfections when bent by hand in as sharp an angle as possible." The specification prohibits edge welding and requires centerbulbs to be compressed or closed when welding to noncenterbulb-type waterstops. The specification also lists the following unacceptable waterstop splicing defects: 1. Tensile strength less than 80% of parent section 2. Free lap joints 3. Misalignment of centerbulb, ribs, and end bulbs greater than 1_16 inch 4. Misalignment that reduces waterstop cross sec- tion more than 15% 5. Bond failure at joint deeper than 1_16 inch or 15% of cross section 6. Misalignment of waterstop splice resulting in misalignment of waterstop in excess of 1_2 inch in 10 feet 7. Visible porosity in the weld 8. Charred or burnt material 9. Bubbles or inadequate bonding 10. Visible signs of splice separation when cooled splice is bent by hand at sharp angle