Waterproof couplings, also known as wall-penetrating couplings or penetration pipes. Flexible waterproof couplings are generally used in structures where pipelines penetrate walls and experience vibration or have strict waterproofing requirements. After partial processing of the coupling, a coat of primer (including camphor lacquer or cold primer) is applied to its outer wall. Waterproof couplings are divided into rigid and flexible types. The main difference between them is their primary application; flexible waterproof couplings are mainly used in places with high requirements such as civil defense walls and swimming pools, while rigid waterproof couplings are generally used in underground pipelines and require pipe架 installation.