Hot and cold-water storage tanks, whether they are used for domestic, commercial or industrial applications, have very specific expectations placed on them when it comes to their need to handle pressured capacities while maintaining the temperature of their contents.

We have, long ago, mastered the means of allowing them to achieve these expectations through the use of highly specialised materials that give storage tanks their unique properties.

These materials, and therefore their associated properties, will change from tank to tank, depending on how they are intended to be used.

Since there is no single-approach to manufacturing tanks that suits every conceivable need, understanding what properties are provided through the right selection of materials used to make up these tanks, will ensure that you invest in one that suits your needs exactly.

Materials will differ from tank to tank, but also with regards to the components that make these tanks up.

For instance, the materials used to construct the vessel itself will differ from those used in the element, and both of which will differ to those materials used to insulate the tank.

So, let’s take a closer look at what they are, and which properties they provide to tanks, depending on how they are intended to be used.

Materials that Make up the Vessel

Let’s start at the vessel, the shell that contains and stores the water itself.

When it comes to the manufacturing materials used in vessels, they need to hold a number of essential properties.

Perhaps the most important property, the one that gives the water tank its actual function, is that is must be- well, water-tight.

A material needs to be chosen, therefore that ensures no leakages.

Secondly, the material needs to be resistant to heat, since the vessel itself is the point where hot water is stored, the presence of heat can, in no way, undermine its structural integrity.

While we are on the point of structural integrity, vessels also need to be able to withstand some fairly extreme pressures if they are to be used safely; with most vessels being able to withstand at least 400kPa.

So which materials allow the vessel to hold these unique properties?

Let’s take a closer look:

Mild Steel

Mild steel is made up of iron which only contains minimal percentages of carbon. It is most commonly used in structural steel, as well as the manufacture of cars, furniture and wire.

Because of its low-carbon content, it is relatively strong when compared to its price, which is quite low in comparison to other alloys.

On top of that, it is also highly ductile, which is why it is commonly used for wire. In the application of vessels for water tanks, this allows it to be fashioned accordingly without any loss in strength or integrity.

The top benefit associated with mild steel is definitely its cost and high resistance to breakage when compared to higher carbon steels which crack when put under the same stresses that mild steel commonly faces.

Stainless Steel

Stainless steel is a popular choice in alloys for a number of applications. It contains percentages of chromium, a material that renders the alloy resistant to tarnishing, corrosion and rust.

It also has the property of being a remarkably hygienic option, which is why it is commonly used for cookware and cutlery and even in surgical and medical equipment.

Because of its strength and exceptional resistance to rust and corrosion, it is also a popular choice as a material for water tank vessels.

Since vessels are in constant contact with water, other alloys might present a problem in terms of rust and corrosion, and stainless steel is one of the best answers to this challenge.

It is, however, a more costly option than mild metals, but it does offer a greater lifespan and less of a requirement for restorative maintenance.

Fully-welded Vessels V.S Rivet Joints

Stepping away a little bit from the actual materials used in their manufacturing, let’s take a moment to look at the significance of how these materials are held together in vessels.

We will take a particular look at the distinction between the process of welding, as opposed to using rivet joints.

Rivet joints, in requiring a series of holes on the vessel, naturally offer less strength and insulation than welded vessels.

They also have a lower threshold for pressure and capacity and will present a reduced lifespan in comparison to welded vessels.

Where water tank vessels are welded, they obviously offer more in terms of the properties mentioned above.

A welded vessel, however, needs to be finalised with extremely high-quality craftsmanship if the tank is to be used safely, especially in higher-pressure units.

The Element

The next materials we discuss will be those used for the element. Because of the way elements operate to massive quantities of water in the least amount of time, considerations need to be made about the conductivity, resistance, strength, efficiency and lifespan of the element.

Fortunately, elements are nothing new to us. They are widely used in everything from heaters to kettles, and their function when it comes to water tanks is exactly the same; albeit at greater capacities and under far more pressure.

Because of the abovementioned needs, elements of all shapes and sizes are typically made from nickel-plated copper.

Let’s take a closer look at the properties this gives to the element in tanks:

Nickel-Plated Copper

As you may have guessed from the name, nickel-plated copper elements have a copper wire core. Copper is the material of choice here for a number of reasons:

Firstly, it offers exceptional levels of thermal and electrical conductivity, making it both effective and efficient when it comes to producing large volumes of heat; especially when used to heat water.

On top of this, copper is also quite malleable and ductile, which means that it is fairly easy to manufacture, and therefore quite cheap in comparison to other, less effective alloys.

Since copper offers everything needed in terms of efficiency, effectiveness and malleability, why then does it need to be nickel-plated?

Since copper is highly conductive and is usually used in conjunction with other alloys when applied to water tanks, it is also at risk of corrosion.

Nickel plating offers resistance to this, quite effectively.

Nickel plating also extends the lifespan of the element thanks to its adhesive properties, which essentially act as a coating for the copper element, ensuring that it can endure extended use.


The last set of materials we will discuss when it comes to their use in hot and cold-water tanks, are those used to provide them with insulative properties.

Whether the tank is being used to store hot or cold water, insulation is critical to its ability to ensure that favourable temperatures are maintained throughout their use.

Where it comes to tanks that are used to store and heat water, thermal insulation ensures that the tank suffers minimal heat loss during use, which keeps the water hotter for longer.

This, in return, means that properly insulated water tanks are more energy-efficient, since they won’t have to heat their contents as frequently.

Let’s take a closer look at the materials that are most commonly used to insulate these tanks:

Fibreglass Wool Cladding

Fibreglass is a material that is commonly used for insulation, whether that be in homes or over boilers and hot-water tanks.

It is found just about everywhere and is made up of plastics that has been reinforced by small glass fibres.

As a result, fibreglass is quite strong, but more importantly, this composition gives it remarkably effective insulation properties.

It dissipates heat very effectively thanks to its glass fibres. In addition to this, its fabrics offer low levels of thermal expansion which result in improved thermal conductivity.

This alone makes fibreglass wool cladding the ideal solution for insulation applications of all types.

It is also a remarkably cost-effective material, which makes for a more affordable water tank, without having to compromise on its insulative quality.

Galvanised Sheet Metal

Galvanised sheet metal is also used as an important insulating component in tanks. This is because they hold a number of unique properties that improve thermal insulation and even the condition of the overall product.

Galvanised metal is created by repeatedly dipping metal sheets in molten zinc. This gives the metal a number of unique properties.

These properties include improved insulation effectiveness, especially when combined with fibreglass wool cladding.

Additionally, galvanised sheet metal is also resistant to heat and corrosion, making it ideal for meeting the challenges of manufacturing tanks that might be at risk to galvanic corrosion.

The insulation properties of galvanised metal are thanks to its enhanced thermal conductivity of zinc which coats the galvanised steel.

This significantly improves how effectively the alloy insulates water tanks.


Aluminium cladding happens to be one of the most frequently used types of insulation materials on the market, although it is most commonly used for cladding in building exteriors.

It offers both an aesthetic appeal and a functional, effective approach to insulation; so, this is no surprise.

It is also remarkably durable and will last a very long time, is completely resistant to corrosion, is 100% recyclable, and offers an economical approach to insulation.

Aluminium cladding is also remarkably lightweight, and it does this without sacrificing on strength or functionality.

For all these reasons, aluminium cladding is a fine option for insulation on water tanks, in place of fibreglass.

Much like aluminium cladding, stainless steel cladding provides an alternative material for insulation on water storage tanks.

Since each of these materials offers slightly different thermal properties to one another, and when comparing their other unique properties, the insulation material that you choose to go with should depend on your needs, the environment the tank will operate in, as well as what you are willing to spend on it; both in terms of investment and upkeep.

Stainless Steel Cladding

Stainless steel offers many of the same properties and benefits as aluminium cladding. It is often, however, a bit pricier than aluminium, but it offers the added benefits of improving the structural integrity of whatever it is applied to.

In addition to this, it is a much greener option than aluminium (even though they can both be recycled), since it requires far less energy for its production.

It is also a more hygienic option and is also far easier to maintain than other alloys, aluminium included; making it an excellent choice for insulation materials in the long-run.

Selecting a Water Tank that Suits Your Needs

With all this information you might be wondering which materials would suit you best when opting for a water storage tank. There is no straight answer to that question, but by understanding your needs and abilities, you can select a material that suits you best.

So, when selecting materials for your tank, consider the following:

  • What are you willing to spend?
  • What capacities does the tank need to hold?
  • How much pressure will the tank need to operate under?
  • What are the specific needs of the facility or building where the tank is being used?
  • How long are you planning on using the tank for?
  • Will you be using any accessories or attachments with your water tank?
  • What are your needs for thermal conductivity?

Contact the Cape Boiler & Heater Company for Details

If you are in the market for a water tank, whether it be for industrial, commercial or domestic use, our team at the Cape Boiler & Heater Company have you covered with specialised offers and bespoke solutions designed to meet your needs.

Be sure to get into contact with one of our representatives today for further details on our offers, or visit our website today for information.