Water Tank Plastic Repair Welding
Plastic Welding helps the environment
Repair of plastics is a reality and can be completed with relative ease.
What is Extrusion welding ?
This is one of the processes used to weld thermoplastic materials. It was developed in the 1960’s as an evolution of hot air welding.
The process uses a welding head (welding shoe) that has a nozzle for hot air and a plasticizing chamber (barrel) that pushes filler material (welding rod) out through the welding head (welding shoe). The process entails heating of the joint surfaces by means of heat of and addition of molten or plasticized filler material (extrudate) being extruded through a die (welding shoe). The extrudate is applied with pressure to ensure good bonding, and then the part is allowed to cool.
In general, an exruder welder is used on materials with a wall section thickness 10mm or larger. Below 10mm wall section thickness a standard Hand Held Hot Air Welding Tool can be employed. In fact most users of extruder welders will also have and use a Hand Held Hot Air Plastic Welding Tool, for small finishing welding jobs.
Extruder Repair Welding – Water Tank
Watch a structural repair of a damaged water tank. An Extruder Welder is used together with a hand held welder.
Frequently asked questions about plastic water tank repair
What plastic are most water tanks made of?
Most rural rotomoulded water tanks in NZ are PE-HD (high-density polyethylene, recycling code 2). Smaller domestic tanks may be PE-MD or LDPE. The recycling stamp on the tank confirms — most have it moulded into the lid or near the inlet.
Can I weld a leaking water tank without emptying it?
No — the tank must be empty and the area being welded must be dry. Welding wet plastic produces inconsistent welds and steam-related defects. Drain the tank, dry the weld area with a clean cloth and let it sit briefly before welding.
Will the welded repair hold water pressure?
Yes, when done correctly. A properly executed PE-HD weld reaches 80-100% of parent material strength. For larger structural cracks, weld from both sides and consider reinforcement. See our guide on plastic weld strength for the data.
Do I need an extruder welder or can I use a hand-held?
For tank wall thickness under about 6mm — a hand-held hot-air welder with PE-HD rod is fine. For thicker walls or large structural cracks, an extruder welder produces stronger welds in less time.
How long will the repair last?
A well-executed PE weld is permanent — there’s no degradation mechanism specific to the weld. UV exposure can affect the surface over years; using UV-stabilised black PE rod for outdoor tanks helps with longevity.
