Waterproof casing, also known as wall casing or wall pipe, is a hardware accessory used for pipes to pass through the walls of buildings with vibration or strict waterproofing requirements. They are divided into two types: rigid and flexible. Flexible casing is mainly used in high-demand areas such as containment walls and swimming pools, while rigid casing is often used in underground pipes.

Flexible waterproof casing is suitable for pipes passing through walls of buildings with vibration or strict waterproofing requirements. The manufacturer produces this accessory according to standard drawings developed by the Institute of Building Sciences. Rigid waterproof casing is a steel pipe with a flange installed in the wall, used for general pipe penetration through the wall to facilitate wall waterproofing.

Waterproof casings are widely used in construction, chemical industry, steel, tap water and sewage treatment units. The most obvious differences between rigid and flexible sleeves are appearance and length. Waterproof casing can be divided into many types, such as steel flexible waterproof casing, double-sided protection rigid closed casing, flexible closed casing, extended flexible waterproof casing and stainless steel waterproof casing.