Introduction to the Revised Standards for Water Storage Tanks
In Kathmandu, a significant development has taken place in the realm of water storage solutions. With an increasing number of households adopting rotational moulded polyethylene water storage tanks, concerns about their quality have grown. In response, the Nepal Bureau of Standards and Metrology (NBSM) has undertaken the task of revising and proposing new standards to ensure the safety and reliability of these products.
The existing standard, introduced back in 1995, was voluntary, meaning that only manufacturers who obtained the Nepal Standards (NS) certification were required to adhere to its specifications. This change is aimed at addressing the growing concerns around the potential health risks associated with substandard products.
The Importance of the New Standard
Anil Shakya, the director at NBSM, highlighted the dangers of microplastics and nanoplastics leaching into stored water when plastic tanks degrade due to prolonged exposure to heat and sunlight. "The revised standard has been prepared to ensure consumers have access to safe drinking water and are not deceived by substandard products," he emphasized.
One of the key features of the revised standard is the inclusion of a migration test. This test determines whether plastic particles can leach from the tank material into stored water during use. The process involves exposing the material to distilled water or a food simulant under specified temperature and time conditions before analyzing the liquid for plastic particles.
Testing Procedures and Compliance
The bureau conducts the test during the manufacturing process for companies seeking Nepal Standard certification. Manufacturers are also required to carry out the prescribed tests during production, while the bureau conducts market surveillance by collecting samples from factories and retail outlets.
Currently, polyethylene water storage tanks are not covered under Nepal's mandatory certification system, allowing manufacturers to produce and sell them without complying with the Nepal Standards. To address this gap, the bureau formed a committee comprising representatives from its technical divisions, engineering campuses, and water tank manufacturers.
Specific Requirements and Materials
The proposed revised standard specifies that the density of polyethylene used in water tanks should range between 932 and 943 kg per cubic metre. For outdoor use, water tanks must be manufactured from carbon black compounded polyethylene, with a carbon black content ranging between 2 and 3 percent. The dispersion of carbon black must meet the testing procedures prescribed under the Nepal Standards.
Manufacturers are allowed to use no more than 10 percent of their own reworked material generated during the production of tanks made under the same standard. However, the use of recycled plastic waste or reprocessed material from any other source, as well as fillers, is prohibited.
Quality and Safety Measures
The polyethylene resin used to manufacture water tanks must be rotational moulding grade and stabilised with antioxidants. These antioxidants, which must not exceed 0.3 percent of the finished resin by mass, should be physiologically harmless and selected from the list approved under the Nepal Standards.
The proposed standard further requires that the tank body, lid, and fittings that come into contact with water must not impart any taste, colour, or odour to the water, nor have any toxic effects that could make it unsafe for consumption.
Design and Manufacturing Specifications
The draft allows manufacturers to produce single-layer or double-layer rotational moulded polyethylene tanks. For double-layer tanks, the inner layer must be white, while the outer layer must be black and account for at least 50 percent of the total wall thickness. "The white inner layer makes it easier for consumers to see whether the stored water is clean or contaminated," said Shakya.
International Testing Methods
The revised draft incorporates five internationally recognised testing methods that manufacturers will be required to follow to ensure product quality and safety. These methods are essential for maintaining high standards and ensuring that the products meet global benchmarks.
Industry Response and Future Outlook
Manufacturers have welcomed the revision, stating that the previous standard no longer reflected advances in production technology and quality requirements. Pulkit Jain, director of Hilltake Group, expressed his support for the proposed revisions. He mentioned that his company has been producing water tanks in accordance with the Nepal Standards and supports the proposed revisions.
Jain argued that compliance should no longer remain voluntary because of the direct implications for public health. "Most households consume water stored in plastic tanks, so the government should make the standard mandatory," he said. He also pointed out that many consumers are purchasing water tanks that do not carry the Nepal Standards certification and are of poor quality.
According to the bureau, eight manufacturers had obtained the NS certification for polyethylene water storage tanks as of mid-April. These include Hilltake Industries of Morang, Kishan Pipe Products of Nawalparasi, Dakshinkali Plastic Industries of Jhapa, Nawa Nepal Plastic Industries of Rupandehi, Rijalco Polytank Industries of Sunsari, Om Panchapuri Industries of Banke, Nepal Sintex Industries of Chitwan, and Gyani Poly Tank Industries of Rupandehi.
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