PVC WATERSTOP WELDING METHODS – Clevcon [Thailand] Co., Ltd.

In concrete structures exposed to water, such as swimming pools, underground water tanks, basements, retaining walls, and tunnels, joints between concrete sections, including Construction Joints and Expansion Joints, are particularly vulnerable to water leakage. This is because these areas may experience movement or changes in the joints between concrete structural elements.

PVC Waterstop is a specially designed material used to prevent water from passing through structural joints. It is embedded within the concrete during construction, forming a watertight barrier that helps minimize the risk of water leakage through these joints.

1. How Many Methods Are There for Welding PVC Waterstop?
Generally, PVC Waterstop joints can be welded using two main methods, depending on the joint configuration, available tools, and manufacturer’s specifications.

Method 1: Hot Knife Welding

This method uses a heated welding blade to melt the end surfaces of both PVC Waterstop sections before pressing them together while the material is still in a molten state. When the two molten PVC surfaces come into contact, they fuse together through a process known as Thermal Fusion, creating a continuous joint that becomes an integral part of the original material.

Required Equipment

⬣ Hot Knife Welding Tool ⬣ Material Clamps or Holding Fixtures for Alignment ⬣ Heat-Resistant Gloves and Safety Goggles

Required Equipment

⬣ Hot Knife Welding Tool

⬣ Clamps or Holding Fixtures for Proper Alignment

⬣ Heat-Resistant Gloves and Safety Goggles

Illustration:
Preparation of the Hot Knife Welding Equipment

1.1 Prepare the Hot Knife Welding Equipment: Turn on the welding tool and allow the heated welding blade (Hot Knife) to reach an operating temperature of approximately 120–150 °C. Wear heat-resistant gloves and safety goggles before operation.

Illustration:
Melting Both Material Surfaces

1.2 Melt Both Material Surfaces: Simultaneously press both ends of the PVC Waterstop against the heated welding blade to ensure uniform melting across the entire cross-section.

Illustration:
Melting Both PVC Waterstop Surfaces

1.3 Immediately Join Both Sections: Remove the heated welding blade and immediately press both ends of the PVC Waterstop together while the material is still molten. Align both ends properly, then apply pressure and hold them in place until the weld begins to solidify.

Illustration:
Weld Inspection

1.4 Inspect the Weld: Visually inspect the weld to ensure it is continuous across the entire cross-section, with no visible gaps or voids along the PVC Waterstop joint.

Precaution: The heating temperature and melting time must be properly controlled. Excessive heat may cause PVC degradation or surface scorching.

View the Heatblade product from CLEVCON / Watch the product demonstration video Click Here

Method 2: Hot Air Welding

This method uses a hot air welding gun together with a PVC welding rod to fuse the welding rod with the surface of the material. The process uses heat to soften or melt both the welding rod and the PVC Waterstop, allowing them to fuse together and form a continuous weld seam.

Required Equipment

⬣ Hot Air Welding Gun ⬣ PVC Welding Rod Compatible with the PVC Waterstop Material ⬣ Welding Nozzle for Feeding the Welding Rod ⬣ Heat-Resistant Gloves and Safety Goggles

Required Equipment

⬣ Hot Air Welding Gun

⬣ PVC Welding Rod Compatible with the PVC Waterstop Material

⬣ Welding Nozzle for Welding Rod Feeding

⬣ Heat-Resistant Gloves and Safety Goggles

Illustration:
Weld Inspection

2.1 Attach the Welding Nozzle to the Hot Air Welding Gun: Attach the welding nozzle securely to the hot air welding gun, ensure it is firmly locked in place, and test the hot air output.

Illustration:
Using Clamps to Secure the Joint

2.2 Secure the Joint Using Clamps: Use clips or holding fixtures to secure the PVC Waterstop in place and maintain proper joint alignment during welding.

Illustration:
Securing the Joint Using Clamps

2.3 Weld the PVC Waterstop: Continuously feed the PVC welding rod while applying hot air to the joint area at a temperature of 150–200 °C: to fuse the welding rod with the surface of the PVC Waterstop.

Illustration:
Welding the PVC Waterstop

2.4 Trim Excess Welding Rod: Cut off the excess welding rod using a utility knife or other sharp tool.

Illustration:
Allow to Cool and Inspect

2.5 Allow to Cool and Inspect: Allow the weld to cool and solidify. Then inspect the weld seam to ensure it is continuous, with no cracks or gaps.

Precaution: Select a welding rod that is specifically compatible with the PVC Waterstop material. Using incompatible materials may result in inadequate bonding and subsequent separation.

View the PVC Hot Air Welder product from CLEVCON / Watch the product demonstration video here

The welding method should be selected based on the type of PVC Waterstop, the joint configuration, and the manufacturer’s recommendations. Do not use any welding method without first verifying its suitability for the material.

2. Weld Quality Inspection (Quality Inspection)
After completing the welding process, the weld quality should be inspected before installing the PVC Waterstop or pouring concrete over it to prevent potential problems in the future.

⬣ Visual Inspection Check whether the weld seam is continuous and uniform. There should be no cracks, gaps, air bubbles, or areas scorched by excessive heat.

⬣ Check Material Shape and Alignment Ensure that the side ribs (Ribs) and center bulb (Center Bulb) are properly aligned and not twisted, bent, or deformed during the welding process.

⬣ For Projects with High Quality Requirements Additional testing, such as a tensile test (Tensile Test), should be performed in accordance with the standards and acceptance criteria specified by the project.

3. Precautions for PVC Waterstop Installation
Even when the welds are properly completed, correct installation of the PVC Waterstop is equally important.

⬣ Secure the PVC Waterstop in the correct position according to the engineering drawings.

⬣ Avoid unnecessary cutting, twisting, or folding of the material.

⬣ Ensure that the PVC Waterstop does not move during concrete pouring.

⬣ Take care to prevent damage from reinforcing steel, formwork, or construction equipment.

⬣ Always check the continuity of the PVC Waterstop before pouring concrete.

Welding PVC Waterstop is a key factor in ensuring effective PVC Waterstop installation. There are two main welding methods:
Hot Knife Welding and Hot Air Welding.

Both methods can be selected according to the joint configuration and site conditions. Proper installation and quality inspection at every stage help increase confidence in preventing water leakage in structures.

Clevcon Thailand Co., Ltd.

Address

Shop