According to the survey done by Utah State University Buried Structures Laboratory, approximately 10% of the total length of water mains in USA were studied and reported about 1 million miles of pipe broken down during service. Table shows that classified by pipe material, Cast Iron pipe has the largest quantity of number of failures which is 8204 of 12963 failures totally. The failure rate of cast iron pipe is also higher than the other material followed by steel pipe, concrete pressure pipe, PVC pipe and ductile iron pipe.
AWA also publish report predicts that more than $1 trillion will be cost on the replacement and repair for pipes over next couple of decades. The cost and expense by failed pipe includes:
- Repair cost
- Leakage cost
- Replacement cost
- Pumping cost and hydraulic efficiency
- Corrosion cost
- Customer service rebate and penalties due to
failures
- Blowout holes --- usually caused by corrosion
- Circumferential cracking --- most common failure
mode for small diameter cast iron pipe usually caused by bending force
- Bell splitting --- caused by different thermal
coefficient of expansion between two pipe material, usually happens in cold
weather area
- Longitudinal cracking --- usually happens on
large diameter pipe which caused by external loading or internal water pressure
- Bell shearing --- caused by compression force
and bending force
- Spiral cracking --- caused by the combination of
internal pressure and bending force
- Corrosion
- Manufacturing flaws
- Excessive forces
- Human error
- Multiple event failures