Impurities are introduced into drinking water through corrosion in water mains. Water that contains heavy metals such as lead may fail to comply with the requirements of the Safe Drinking Water Act and other regulations. The usual remedy for this situation at U.S. Department of Defense (DoD) facilities is to replace the corroded pipes or to use bottled drinking water. This project validated an alternative remedy with the in-place application of a chemically resistant, non-toxic epoxy coating developed by the Naval Research Laboratory as an interior pipe lining to prevent leaching of metal impurities.
Compressors were used to blow hot, dry air and abrasive garnet grit through the drinking water distribution systems to remove rust and other contaminants. Hot, compressed air was then used to deposit a two-component epoxy coating on the interior of the pipes. Subsequent hardening of the coating in a stream of hot air took approximately 20 minutes. The distribution systems were then flushed with water and returned to service within 72 hours. Sampling and testing of the distribution systems before and months after installation showed that lead remained below Environmental Protection Agency (EPA) drinking water standards. Thus, the method was effective in preventing the leaching of lead.
This fast, innovative, in-situ lining technique will allow the DoD to comply with Federal regulations and cost-effectively rehabilitate drinking water distribution systems aboard ships and at shore facilities around the world. Installation costs were estimated at $75 per linear foot, and typical savings when compared to pipe replacement were approximately $100,000 for a two-story, 40-unit apartment building.
The system causes minimum disruption to facilities or their occupants, is suitable for pipes inside buildings and underground, and may be used on pipes as long as 1,000 feet despite numerous bends or varying pipe diameters. It is approved by NSF International, the sole firm authorized by the EPA to test and approve materials for contact with drinking water. To eliminate interference with the coating process and to prevent lining failure, residual rust must be completely removed prior to application. Once properly installed, the lining requires no maintenance and has an expected lifetime of 30 years based on previous sanitation applications in aircraft carriers. (Project Completed - 1997)