WHY ARE PLASTIC PIPES FAILING IN HAWAII?

A CASE STUDY 

The following case study is the property of Plastic Expert Group and cannot be copied or distributed without prior permission. Our case analysis does not imply that this specific plastic failure will happen systematically. Every case is unique and should be treated accordingly. 

PROBLEM: 

PLASTIC PIPE FAILURES IN HAWAII

In recent years many condominiums and hotels have been constructed in Hawaii using plastic piping for fire suppression and potable water systems. Unfortunately, unless the pipe is manufactured properly and installed precisely following installation instructions, pipe failures frequently occur causing significant property damage. 

There are two primary piping systems used during the construction of condominiums and hotels – especially in Hawaii.

Fire Sprinkler Pipe

The plastic pipe used for fire sprinkler piping systems is CPVC. Unfortunately, CPVC is prone to failure when it is improperly installed using products containing chemicals that are not CPVC compatible, such as, for example, acoustical or fire stop caulks containing ester plasticizers. If CPVC pipe is used for potable water, some piping systems turn brittle after a few years of service. For example, in hotels, when housekeeping personnel accidentally bump the toilet tank fill valve, if the pipe has turned brittle, the valve will break from the pipe at the wall penetration. We have determined the cause of rapid CPVC pipe embrittlement. If excessive solvent cement is used during formation of joints in the piping system, the solvents in the cement are absorbed by the plastic causing the plastic to soften. Once the piping system is placed under water pressure, the long chain plastic molecules in the softened pipe become separated causing the plastic pipe to turn brittle and break.

Potable Water Pipe

The most common plastic pipe used in recently constructed Hawaiian condominiums and hotels for potable water is PEX. Unfortunately, PEX is degraded when exposed to hot chlorinated water unless the pipe is manufactured properly by the addition of high levels of antioxidant stabilizers.  In most condominiums and hotels, hot water piping systems are recirculated so that the piping is always exposed to hot chlorinated recirculated water. This is an extremely demanding environment. Since PEX is an inherently oxidizable plastic, in order for the pipe to survive for decades, high levels of antioxidant stabilizers must be mixed into the plastic. Since antioxidants are small chemicals that are partially soluble in hot water, the antioxidants are extracted from the inside surface of the pipe. Once the antioxidants are depleted, the inside surface of the PEX pipe turns brittle allowing cracks to develop which propagate through the wall of the pipe.