Potable vs. Non-Potable Water Storage: Choosing the Right Tank

Table of Contents

• Introduction

• What Are Potable Water Tanks?

  • Standards and Certifications

  • Material Requirements

  • Applications

• What Are Non-Potable Water Tanks?

  • Guidelines and Requirements

  • Material Flexibility

  • Applications

• Key Differences Between Potable and Non-Potable Tanks

• Practical Considerations for Choosing a Tank

• Maintenance and Safety for Both Tank Types

• Conclusion

• Recommended Visuals

• Comparison Table

Introduction

Water storage tanks are essential for various applications, from providing drinking water to supporting irrigation and industrial processes. However, not all tanks are created equal. Potable water tanks are designed to store water safe for human consumption, adhering to strict health standards, while non-potable water tanks are used for non-drinking purposes like irrigation, with fewer regulatory requirements. This blog post explores the differences between these tank types, their standards, materials, applications, and practical considerations to help you make an informed choice.

What Are Potable Water Tanks?

Potable water tanks are designed to store water that is safe for drinking, cooking, or other human consumption needs. These tanks must meet rigorous health and safety standards to ensure the water remains uncontaminated and free from harmful substances.

Standards and Certifications

Potable water tanks are subject to strict regulations to protect public health:

• United States:

  • NSF/ANSI Standard 61 (NSF 61) certifies that materials, coatings, and components in contact with drinking water do not leach harmful substances.

  • AWWA (American Water Works Association) standards provide guidelines for design and maintenance:

    • D102: Coating Steel Water Storage Tanks.

    • D104: Cathodic Protection for Steel Water Tanks.

    • D110: Prestressed-Concrete Water Tanks.

    • D130: Flexible Membrane Linings for Potable Water Storage (AWWA Standards).

  • AWWA Manual M42 recommends draining and inspecting tanks every three years to maintain water quality.

• United Kingdom:

  • WRAS (Water Regulations Advisory Scheme) approval ensures tanks comply with regulations for safe drinking water storage (WRAS).

• Australia:

  • AS/NZS 4020 tests products for suitability in contact with drinking water, ensuring no adverse effects on water quality (Australian Standards).

  • AS/NZS 4766 specifies requirements for polyethylene tanks used for water storage.

These standards ensure that potable tanks maintain water safety throughout their lifespan.

Material Requirements

Potable water tanks must be constructed from non-toxic materials that do not contaminate the water:

• Common materials include fiberglass, stainless steel, and polyethylene with food-grade linings.

• Tanks often feature NSF-certified coatings or linings to prevent leaching of chemicals.

• Designs include features like sealed lids, screened vents to prevent insect entry, and insulation to regulate temperature and inhibit microbial growth (Tricel Water).

Applications

Potable water tanks are used in scenarios where safe drinking water is critical:

• Municipal water supply: Storing treated water for communities.

• Rural and remote areas: Providing drinking water where tap water is unavailable.

• Emergency response: Supplying potable water during disasters.

• Residential use: Storing water for households not connected to mains water.

What Are Non-Potable Water Tanks?

Non-potable water tanks store water that is not intended for human consumption, such as for irrigation, industrial processes, or greywater systems. These tanks have fewer regulatory requirements since the water does not need to meet drinking water standards.

Guidelines and Requirements

While non-potable tanks do not require drinking water certifications, they may still need to comply with guidelines for specific applications:

• International Plumbing Code (IPC): Chapter 13 outlines requirements for non-potable water systems, including protection against backflow, insect-proofing, and compatibility with stored liquids (IPC Chapter 13).

• UK Guidelines:

  • ACOP L8 and BS8558 address Legionella control in water systems, requiring regular inspections and cleaning to prevent bacterial growth (ACOP L8 Guidelines).

  • Water Supply (Water Fittings) Regulations set requirements for the design and maintenance of non-potable systems to ensure safety and functionality (Tricel Water).

• General Standards:

  • Tanks must be durable and suitable for the intended liquid, with materials resistant to corrosion or degradation.

  • For specific uses like wastewater or chemical storage, tanks may need to meet industry-specific standards, such as those for sludge or anaerobic digesters (American Structures).

Material Flexibility

Non-potable tanks can use a broader range of materials since they do not need to meet drinking water safety standards:

• Materials like polyethylene, fiberglass, or steel are common, but they may not require food-grade linings or NSF certification.

• Some tanks use plastics that could contaminate water if used for drinking, making them unsuitable for potable applications (Oakville Pump).

• Designs may prioritize durability and cost over health safety, depending on the application.

Applications

Non-potable water tanks are versatile and used in various scenarios:

• Irrigation: Storing water for agricultural fields or gardens.

• Greywater systems: Holding water for flushing toilets or washing machines.

• Industrial processes: Storing water for cooling, cleaning, or manufacturing.

• Fire protection: Holding water for firefighting systems (American Structures).

• Rainwater harvesting: Collecting runoff for non-drinking uses like lawn care (Tuffa).

Key Differences Between Potable and Non-Potable Tanks

The primary differences between potable and non-potable water tanks lie in their purpose, standards, and materials:

These distinctions ensure that potable tanks prioritize human health, while non-potable tanks focus on functionality and cost-effectiveness.

Practical Considerations for Choosing a Tank

Selecting the right tank depends on your specific needs:

• Intended Use: If the water is for drinking, choose a potable tank with NSF 61 or WRAS certification. For irrigation or other non-drinking uses, a non-potable tank is sufficient and often more affordable.

• Material Compatibility: Ensure the tank material is suitable for the stored liquid, especially for non-potable tanks holding chemicals or wastewater.

• Regulatory Compliance: Verify that the tank meets local regulations, such as AWWA standards in the U.S. or Water Supply Regulations in the UK.

• Cost: Potable tanks may be more expensive due to stricter material and certification requirements, so consider your budget and whether a potable tank is necessary (Direct Water Tanks).

Maintenance and Safety for Both Tank Types

Both potable and non-potable tanks require maintenance to ensure performance and safety:

• Potable Tanks:

  • Regular cleaning and disinfection to prevent bacterial growth, as per AWWA Manual M42 (every 3-5 years) or ACOP L8 guidelines.

  • Inspections for leaks, secure connections, and contamination risks like algae or sediment (Tricel Water).

  • Temperature regulation to inhibit microbial growth, typically keeping water below 20°C (Wet Services).

• Non-Potable Tanks:

  • Inspections for structural integrity and application-specific issues, such as corrosion in wastewater tanks.

  • Cleaning when necessary to address scale, algae, or sediment, as outlined in BS8558 guidelines.

  • Protection against environmental factors like freezing or insect entry, as per IPC requirements.

Proper maintenance extends the lifespan of both tank types and ensures they perform as intended.

Conclusion

Potable and non-potable water storage tanks serve distinct purposes, with potable tanks designed for safe drinking water and non-potable tanks for non-drinking applications like irrigation. Potable tanks must adhere to strict standards like NSF 61, AWWA, or WRAS, using non-toxic materials to prevent contamination. Non-potable tanks have more flexible material options and follow guidelines like the IPC or ACOP L8, focusing on functionality rather than drinking water safety. By understanding these differences, you can choose the right tank for your needs, ensuring safety, compliance, and cost-effectiveness.