Yes, plastic water tanks, specifically those made from polyethylene, do expand and contract.
Understanding Plastic Tank Expansion
Plastic water tanks, particularly those commonly made from polyethylene, are designed to be robust and hold large volumes of liquid. However, they are not rigid in the same way as metal or concrete tanks. A key characteristic of materials like polyethylene is that they expand and contract. This natural physical property means that the tank's size and shape can change slightly in response to various environmental factors.
Factors Influencing Expansion and Contraction
The degree to which a plastic tank expands or contracts is not uniform and depends on several variables. According to experts, the degree in which this occurs depends on:
- The size of the tanks: Larger tanks have more material and surface area, potentially leading to more noticeable expansion or contraction.
- Wall thickness: Thicker walls can sometimes offer more resistance to changes, but the material's properties still apply.
- Specific gravity (or relative density) of contents: Denser liquids exert more pressure, which can influence the tank's structure and potential expansion under temperature changes.
- Temperature of contents: Warmer liquid inside the tank will transfer heat to the plastic walls, causing them to expand more than if they were holding colder liquid.
- Ambient temperatures: The temperature surrounding the outside of the tank is a significant factor. Plastic expands when heated and contracts when cooled. Significant swings in daily or seasonal temperatures will cause the tank to undergo cycles of expansion and contraction.
Practical Implications of Tank Movement
This expansion and contraction, while often subtle, will affect volume over time. For most standard water storage applications, this volumetric change is minor and doesn't significantly impact the usable capacity.
However, this movement is why proper installation is crucial. Tank manufacturers often recommend:
- Placing the tank on a completely flat, stable surface to prevent uneven stress.
- Using flexible pipe connections where the tank connects to plumbing. Rigid connections could be stressed or even break over time due to the tank's natural movement.
- Allowing some air gap or "ullage" at the top, especially if the contents might freeze (though water expands when freezing, not just from thermal warming).
Understanding that plastic tanks breathe and flex is important for their longevity and safe operation.
[Plastic Tank Properties]
