A Complete Guide to Water Tank Material & Grades

Did you know that not all stainless steel is considered safe? 

After researching online, you may have found that stainless steel is considered the best material for water storage. But how can it not be safe?

Stainless steel is no doubt the best material for a water tank, but not all grades of stainless steel can be considered safe.

So, how will you know which stainless steel grade to choose?

Don’t worry! This blog is a comprehensive guide on the various water tank material grades.

So, let’s dive into understanding common stainless steel grades used in tanks, and which one you should opt for!

Common Stainless Steel Grades Used in Tanks

• SS304 Grade

The first one in the list is SS304. It is the most commonly used austenitic stainless steel grade. 

SS304 is composed of approximately 18% chromium and 8% nickel. It offers excellent corrosion resistance, good formability, and weldability.

Talking about the industry, it performs well in a wide range of environments, including water, food processing, and mild chemicals. 

It resists oxidation up to 870°C but is less suitable for high-chloride conditions. Its mechanical properties, including high tensile strength and elongation, make it ideal for water tanks, kitchen equipment, and architectural applications. 

Affordable and reliable, SS304 is often the first choice for general-purpose stainless steel use.

• SS316 / SS316L

SS316 and SS316L are other popular stainless steel grades. Both these grades have molybdenum and an austenitic structure. 

Added Molybdenum makes stainless steel corrosion resistant, while the austenitic structure ensures strength, ductility, and temperature stability. This combination makes this grade super corrosion resistant to chloride-rich and acidic environments. 

But if they are equally good, what’s the difference between the two?

The key difference lies in carbon content: SS316 has a maximum of 0.08% carbon, while SS316L (the "L" stands for "low") has a maximum of 0.03%. 

This reduced carbon minimises the risk of carbide precipitation during welding, which can otherwise lead to intergranular corrosion.

SS316/316L is widely used in RO water storage, marine environments, pharmaceutical manufacturing, and food processing due to its enhanced resistance to saltwater, harsh chemicals, and sanitizing agents.

Even Beltecno stainless steel water tanks are made up of SS304/SS316L grades, ensuring the best quality water tanks!

• Duplex Stainless Steel 

Duplex stainless steel, just as its name suggests, is a hybrid alloy. It combines the best properties of austenitic and ferritic stainless steels. 

In aggressive environments, especially where exposure to chlorides, acids, or high pressure is common, duplex stainless steel performs well. 

It is highly known for its high strength-to-weight ratio. 

This makes it ideal for demanding applications where both durability and weight savings matter. 

Some of the common uses of these tanks are chemical storage, desalination plants, and offshore structures.

• SS430 

Last but not least in the list is SS430. It is a ferritic stainless steel known for its magnetic properties and lower cost compared to austenitic grades like 304 or 316. 

Ferritic refers to a specific crystal structure of stainless steel, called ferrite, which is primarily made of iron and chromium.

This stainless steel material grade offers moderate corrosion resistance and is thus not suitable for aggressive or high-moisture environments. 

SS430 is best used in non-critical applications such as decorative water tanks, kitchen appliances, or interior architectural features.

Its strengths include good formability and resistance to oxidation at moderate temperatures. 

However, it’s less ductile, not weld-friendly, and can rust in humid or coastal environments, so it's always advisable to use it with caution.

As we have now talked about all the stainless steel water tank material grades, here’s the comparative analysis of these grades for your better understanding. 

Comparison of Grades

Still wondering which one to choose according to your industry? Let’s solve your query and understand which water tank material grade is your industry’s go-to option. 

Industry-wise Grade Suitability

• Food & Beverage Industry

Let’s start with one of the industries where water tank material grade can impact various people’s lives. 

What matters in the food and beverage industry is hygiene and food safety certification. 

SS304 or SS316  are corrosion-resistant, considered food-grade stainless steel and are easy to clean. As it is corrosion resistant and does not leech chemicals, the taste of the content remains unaltered. 

In contrast, SS430 lacks the corrosion resistance, weldability, and hygienic finish required for food safety. Duplex stainless steel is overengineered and harder to fabricate for standard food-grade applications.

Read about: Stainless steel applications in the Food and Beverage Industry. 

• Pharmaceutical Industry

Pharmaceutical industries need ultra-clean and sterile conditions. These conditions are perfectly met by the SS316L stainless steel grade. 

SS316L has a low carbon content that helps reduce contamination and corrosion. While duplex stainless steel is difficult to polish to pharma-grade smoothness, making it harder to clean and validate under ASME BPE standards. 

Its high strength is unnecessary, and complex welding increases contamination risk.

Meanwhile, SS430 lacks the corrosion resistance and chemical durability required in pharmaceutical cleaning processes. It's also not compliant with pharma hygiene standards and can degrade quickly under sanitization.

Read about a case study: Stainless Steel Application in the Healthcare Industry 

• Water Treatment Plants

SS304 is the most common and cheapest stainless steel used in water treatment plant tanks. 

It is good for potable water and standard treatment chemicals. Easy to fabricate and for general-purpose use. 

SS316/316L is used in coastal, humid or chloride-rich environments as it has better corrosion resistance. 

For highly aggressive water chemistries or desalination plants, Duplex stainless steel is best as it has high durability and strength, but at a higher cost. 

SS430 is not suitable as it does not have enough corrosion resistance. So, SS304 is good for most applications, SS316L or Duplex SS for more demanding conditions.

• Data Centers

Talking about data centres, SS304 is good for indoor chilled water or backup storage tanks in a controlled environment.

But in coastal areas or where high humidity and treated water are factors, SS316L is the better choice. 

The added molybdenum gives superior resistance to chlorides, rust and chemical attack, for long-term reliability.  

SS430 doesn’t have enough corrosion resistance, will fail prematurely, and Duplex SS is too complex and expensive for standard data centre use.

You should choose the grades based on the environment, water chemistry, usage and lifecycle.

Read about: Stainless Steel Application in Data Centres

How to Choose the Right Grade for Your Tank

• Assess the Content Stored: The content you’ll be storing inside the water tank matters a lot, so assess the content first. Is it water, chemical, or something corrosive?
  
  
• Understand the Environment: The second step is to understand where you are thinking of placing the tank. Is it indoor, outdoor, coastal, or high-humidity?
  
  
• Budget vs Long-Term Value: Your budget for the water tank also matters. Evaluate the total ownership cost and understand the return on investment.
  
  
• Regulatory Requirements: Every industry, especially the food or pharma industry, requires compliant tanks. So, what does your industry demand food-grade or pharma-grade compliance?
  
  
• Maintenance Capabilities: Is regular cleaning and inspection possible? Understand your maintenance capabilities and frequency.
  
  
• Custom Fabrication Needs: See if your industry or commercial building needs a tank with additional features or customisation. Some SS tank manufacturers like Beltecno provide tailor-made stainless steel tanks for their clients.  

Some FAQs on Tank Material Grades

Q1: Can I use SS304 for drinking water? 

Yes, SS304 is safe, corrosion resistant and commonly used for drinking water storage. Good hygiene, durability and cost-effectiveness are a standard choice for potable water tanks.

Q2: What’s the difference between 316 and 316L? 

316L has lower carbon content than 316, which improves weldability and reduces the risk of sensitization and corrosion at welded joints, good for sanitary or high-purity applications.

Q3: Is SS430 safe for water tanks? 

SS430 can be used in a low-corrosion indoor environment, but lacks the corrosion resistance for long-term or harsh conditions. Good for non-critical or decorative water storage. 

Q4: Which grade lasts the longest in a coastal environment? 

SS316L and Duplex stainless steel are superior to salt-laden air and chlorides, good for long-term performance in coastal or marine environments.

Q5: Can I mix grades in a multi-compartment tank? 

It is technically possible but not recommended; mixing grades can cause galvanic corrosion between different metals and reduce the life and integrity of the tank over time.

Conclusion

The right water tank material grade for your tank is crucial for performance, longevity, and safety. 

Whether it's SS304 for general-purpose use or SS316L for more demanding environments, every grade offers unique advantages based on your specific needs.

If you're unsure which material is best for your application, don’t worry. 

Beltecno is here to help. Our experts will guide you every step of the way, ensuring you get a high-quality, reliable stainless steel tank tailored to your requirements.

Contact Beltecno today for trusted advice and custom tank solutions you can count on.