Complete Guide to Water Storage Tank in the Water Treatment Industry

Water storage tanks are foundational assets within water treatment systems. As regulatory demands tighten and water quality standards rise, selecting the appropriate storage tank is more critical than ever. This comprehensive guide dives deeply into the most common types of water storage tanks used in the industry, detailing their strengths, limitations, applications, and the crucial factors to evaluate when choosing the right solution for your water treatment facility.

Why Water Storage Tanks Are Vital in Water Treatment Systems

Water treatment plants rely heavily on storage tanks to securely hold various types of water — from raw intake water to fully treated potable water, as well as process and wastewater. The performance and longevity of these tanks directly affect operational reliability and water quality control.

Ensuring Water Quality Integrity: Improper tank material or design can lead to corrosion, biofilm formation, or contamination, compromising treated water quality.

Maintaining Process Continuity: Adequate storage capacity and structural reliability prevent interruptions in water supply across treatment stages.

Reducing Operational Costs: Selecting corrosion-resistant and durable tanks lowers frequent repair and replacement expenses over the lifecycle.

Overview of Common Water Storage Tank Types

1. Glass Reinforced Plastic (GRP) Tanks

GRP tanks are constructed from a composite of polyester resin and glass fibers, merging strength with lightweight properties.

Superior Corrosion Resistance: GRP tanks effectively resist chemical corrosion, making them suitable for treated water and industrial process fluids.

UV and Weather Durability: Their resistance to ultraviolet radiation makes them ideal for outdoor installations without protective coatings.

Modular and Scalable: Many GRP tanks feature sectional designs, allowing for on-site assembly and future capacity expansion.

Minimal Maintenance: Smooth, non-porous surfaces resist algae and deposits, easing cleaning requirements.

Common Uses: Potable water storage, rainwater harvesting systems, industrial process water tanks, and wastewater storage applications.

Design Considerations: Proper resin-to-fiber ratios and curing are essential to avoid stress cracks and ensure long-term durability.

2. Galvanized Steel Tanks

These tanks are made by coating steel plates with a zinc layer that protects against rust and corrosion.

Robust Structural Integrity: High mechanical strength suits large-volume storage and harsh mechanical environments.

Cost-Effective Construction: Generally more affordable upfront than stainless steel alternatives.

Ease of Transport and Assembly: Modular panel construction supports onsite assembly for large-scale projects.

Limitations:

Zinc coatings degrade over time, especially in acidic or high-humidity conditions, requiring scheduled inspections and recoating.

Not recommended for storing potable water without an internal lining due to potential contamination risks.

Typical Applications: Industrial water storage, fire suppression reservoirs, and temporary construction water supply.

3. Stainless Steel Tanks

Stainless steel tanks represent the premium tier, combining hygiene, durability, and corrosion resistance.

Outstanding Corrosion Resistance: Austenitic stainless steel grades (304, 316L) provide excellent resistance against a wide range of chemicals and environmental conditions.

Hygienic and Non-Porous Surface: Ideal for potable water and industries requiring stringent sanitary standards such as pharmaceuticals and food & beverage.

Thermal Stability: Can withstand extreme temperatures without compromising structural integrity.

Low Maintenance Over Life Cycle: No need for periodic coatings or liners, resulting in reduced upkeep.

Applications: High-purity potable water storage, pharmaceutical water treatment systems, food and beverage production facilities.

Specification Tips: Select steel grade based on water chemistry and regulatory requirements to optimize corrosion resistance and safety.

Factors to Consider When Selecting Water Storage Tanks

1. Water Quality and Intended Use

The nature of the stored water directly impacts tank material choice due to health and safety regulations:

Potable water: Requires materials certified safe for human consumption. Stainless steel (grades 304 or 316L) and GRP tanks meet NSF/ANSI 61 standards for drinking water safety, with low leachate risk. Studies show stainless steel tanks maintain water quality with less than 0.1 CFU/mL bacterial contamination over 12 months, compared to up to 10 CFU/mL in poorly coated steel tanks.

Industrial/process water: Can tolerate less stringent materials; galvanized steel tanks are often used. However, galvanizing coatings typically last 10-15 years under normal conditions before corrosion reduces integrity, per ASTM A123 standards.

2. Environmental Conditions

Exposure to sun, temperature fluctuations, and weathering affect tank durability:

UV resistance: GRP tanks typically resist UV degradation with a service life of 20+ years in full sun exposure, verified by accelerated weathering tests (ASTM G154).

Temperature range: Stainless steel tanks endure from -40°C to 400°C without material compromise, while galvanized steel’s effective range is -20°C to 80°C.

Rain and humidity: Corrosion rates in galvanized steel increase significantly in coastal or high-humidity areas—up to 5 times faster than inland dry zones—according to corrosion monitoring studies. GRP and stainless steel exhibit negligible corrosion in such environments.

3. Chemical Composition and Corrosion Risk

Water pH, presence of chlorine, sulfates, or acids influence tank lifespan:

pH range: Stainless steel resists corrosion effectively in a broad pH range (2–13), while galvanized steel is best suited for neutral to mildly alkaline waters (pH 6.5–8.5).

Chloride concentration: Chloride ions above 200 ppm accelerate pitting corrosion in stainless steel; thus, 316L grade or special passivation is recommended.

Chemical additives: GRP tanks tolerate exposure to many aggressive chemicals (e.g., ferric chloride, caustic soda) where steel tanks fail. According to chemical resistance charts, GRP can last 25+ years with regular inspections in such environments.

4. Capacity and Flow Requirements

Correct sizing ensures operational efficiency and emergency preparedness:

Storage volume: A general guideline recommends tanks hold 1.5–2 times the average daily water consumption to accommodate peak demands and maintenance downtime. For example, a municipal plant with daily flow of 10,000 m³ should consider a tank capacity of 15,000–20,000 m³.

Flow rates: Tank inlet/outlet sizing should match treatment plant flow rates (e.g., 2,000 L/min) to prevent bottlenecks. Hydraulic modeling tools can optimize sizing for system pressure and turnover rates.

Emergency reserves: NFPA standards for fire water tanks recommend reserves of 90 minutes of fire flow, which might add 50-100% additional capacity depending on local codes.

5. Maintenance Resources and Frequency

Ongoing upkeep impacts total lifecycle cost:

Inspection intervals: Galvanized steel tanks require corrosion inspections every 6 months; GRP and stainless steel tanks typically require annual inspections.

Cleaning frequency: Potable water tanks are cleaned every 3–5 years to prevent biofilm buildup, supported by CDC water safety guidelines.

Repair costs: Re-galvanizing costs range from $10 to $20 per square foot; patch repairs for GRP tanks cost approx. $200–$500 per repair, stainless steel repairs often require welding and passivation services, costing $500–$1,000 per event.

The Imperative of Corrosion Resistance

Corrosion is a leading cause of tank failure and water contamination in storage systems. Tanks made from corrosion-resistant materials like GRP, galvanized steel with protective coatings, or high-grade stainless steel ensure operational longevity, safeguard water quality, and minimize costly downtime.

Conclusion

Selecting the optimal water storage tank is a strategic, long-term decision affecting operational efficiency, safety, and total cost of ownership in water treatment operations. GRP tanks excel in chemical resistance and modular installation; galvanized steel tanks provide economical strength for industrial applications; stainless steel tanks deliver superior hygiene and durability for sensitive uses.

Understanding the specific benefits and trade-offs of each tank type empowers water treatment professionals to tailor their storage solutions to their precise needs. For best results, engage with experienced suppliers offering corrosion-resistant tanks engineered specifically for water treatment applications.