The Water Tanks Assembly Process

The Water Tanks Assembly Process

The Water Tanks Assembly Process

Water tank services is delivered to site and a site assessment is completed it is time for assembly. First and foremost the ground where the tank is being installed has to be assessed including whether it needs a concrete base.

Both rotational and blow molding use a mold to shape plastic water tanks. But, how the molten plastic polymer is inserted into the mold differs between the two processes.

Rotational Molding

From pink yard flamingos to dump truck beds and hundreds of products in between, rotomolding is an efficient manufacturing process. This fabrication method creates strong, long lasting products that are highly resistant to deterioration due to chemicals or environmental stresses.

During the rotational molding process, powdered polymer resin is loaded into a hollow mold coated with a release agent. The mold is then slowly rotated as the resin heats up, coating the entire tool with a thick layer of molten plastic.

Unlike other molding processes, rotational molding produces a single part rather than multiple parts requiring additional downstream processing steps. This results in less wasted polymer resin in the form of runners and sprues. Additionally, it allows for more intricate designs to be made without adding additional costs associated with a second step of trimming and stripping. The molded product may also include draft angles to help ease removal from the mold as well as compensate for shrinkage during the cooling process.

Blow Molding

Water tanks are made with a wide variety of components, additions and materials to suit specific purposes. These can include commercial storing of household water, industrial storing for manufacturing, agricultural and irrigation.

The blow molding process is similar to injection molding in that molten plastic is injected into a mold, but the way the preform takes shape is different. In injection molds, the preform is a tube-like piece of shaped plastic polymer called a parison. This is inserted into the mold with one end sealed, and the other is left open to receive compressed air. The air inflated the parison against the mold walls, and the product is ejected when it cools.

In injection stretch blow molding, a grey rod elongates the preform and expands it to the mold wall height. The mold is then closed, the parison is removed and the completed plastic water tank is ejected. Both processes can produce very precise and detailed products, although injection molding has a slight edge in terms of wall thickness uniformity.

Heat Treating

Tanks used for process water have to be treated differently than residential and commercial tanks. They require more corrosion resistance and inertness, so they’re coated with a special coating to protect the internal structure. Coatings like the GFtS coating offered by Permastore are the ideal solution for process water tanks because they’re highly inert, corrosion resistant and do not require recoating.

During the assembly process, it’s important to ensure the right size pipes are used when connecting the tank to the inlet and outlet pipes. Also, it’s vital that any bulkhead drain and vent fittings are tightened properly to avoid leakage. When tightening, do so with care because excessive tightening can cause thread stripping and cracking in the tank’s valves and fittings.

It’s also a good idea to strategically install sacrificial anodes near the tank inlet and outlet connections as this will reduce plumbing runs and maintenance costs. These anodes should be checked every 12 months.


The cooling process involves two primary mediums: water and air. Each has its own physical characteristics that impact its cooling capabilities. These include specific heat, density and thermal conductivity. Water has higher specific heat and density than air, which allows it to absorb more heat and stay cool longer.

Water is piped into the tank and circulated. This keeps the water in perpetual motion so it doesn’t flash to steam and lose its coolness. This system is a necessity in many regions where water scarcity is prevalent.

Once the tank is installed and plumbing connections made it is ready to use. At this point, the site needs to be prepared, including digging a hole that is at least as large as the tank, leaving a 150 – 200 mm gap in the walls of the hole and back filling with soil that has been sifted and stabilised. This will ensure that the ground can support the weight of the tank and prevent damage to its lining or insulation.

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