Dairy farmers will need more time to upgrade milk cooling systems to align them with proposed new regulations.

New milk cooling regulations applying from June 1, 2018 mean the countdown is on to ensure systems are up to speed.

Having a water tank at home is very important these days. But because there are too many types of water tanks, people can sometimes become confused as to which of these tanks to choose. Water tanks have become available in different materials including plastic, steel, fiberglass and concrete. While all of these are suitable for any house or office, one must be aware if it complies with the requirements of AS/NZS4020. Steel Tanks Steel is a common material used in manufacturing water tanks. Although steel rainwater tanks are tough, they are also prone to corrosion. Steel tanks are mostly coated with rust resistant coatings such as zincalume. Brand new steel tanks usually need to be flushed before they can be used. This is because these tanks mat leak excess concentration of zinc, which may not be deadly, but could affect the taste of stored rainwater. The most common material used in manufacturing steel tanks is galvanised steel, which is basically applying zinc to steel. These steel tanks are commonly joined using a hot iron to combine lead and tin on the joint of the steel. Like other types of steel, galvanised steel is not resistant to corrosion so manufacturers also need to apply rust-resistant coatings to these tanks. Steel tanks fabricated for water storage do not have corrosion issues like galvanised steel tanks. However, they cost more than plastic coated tanks and galvanised steel tanks. Steel normally have a warranty period of about 20 years, however, the manufactured product or steel water tanks only have a 10-year warranty on a pro-rata basis. Should you choose this type of tank, it is very important that you read the warranty guidelines carefully. Concrete Tanks Another popular material used for manufacturing tanks is concrete. Concrete tanks are usually very heavy, difficult to transfer and install. Normally, an 18,000 litres concrete tank would weigh about 8.81849 tons. Large concrete tanks are often installed underground, while smaller tanks can be installed above ground. Small tanks are commonly delivered complete, while medium and large tanks are poured on site. Concrete tanks are delivered in 3 pieces and the openings are covered by rubber or synthetic sealing ring. A sealant is applied to the inside part of the tanks at the join. This stops the water from leaking out. New concrete tanks may affect the taste of stored water and may leak lime, which increases the pH level of stored water. Therefore, it is advisable to flush these tanks before using them. Common issues with concrete tanks include cracking and leaking. What repairmen do is to drain the tanks completely or to the portion of the crack and use a sealant to repair the damage. Sometimes, a plastic liner needs to be used in order to repair extensive damages to the tank. Such cases can be a bit expensive. Fibreglass Tanks Fibreglass tanks are manufactured using a food-grade coating on their interior surface. It usually takes time for this coating to be cured, so production also takes a bit of time. But the wait is worth it. One good feature of fibreglass is that it’s very rigid, which means that the wall of the tank can be thin to manage water pressure. Fibreglass tanks are often manufactured with resin mixed with a hardener. Along with the glass fibres, the catalyst or hardener is sprayed on to a mould by an operator. Doing this makes these tanks sturdier. However, this process is dependent on individual skill, which results in a variation from tank to tank. Like concrete tanks, fibreglass tanks are also prone to cracking and leaking. Since fibreglass allows light to pass through it, algal growth is also possible. However, to prevent this from happening, manufacturers use a black covering inside these tanks or they are often painted on the outside. Some of these tanks are designed with sufficient pigment to address this issue. Plastic Tanks Plastic tanks are the most popular types of the water tank in New Zealand. Mostly, these tanks are many of food-grade polyethylene plastic to comply with AS/NZS4020. Polyethylene is not prone to corrosion, which means longer life for plastic tanks. This also means that plastic tanks are lightweight, easy to transport and easy to install. Plastic tanks are also inexpensive compared to other tanks. There’s no need for heavy equipment to install them. They are manufactured and delivered in one piece, so you don’t need sealants during installation. Polyethylene is also a tough material, which allows people to bury it at depth or install them above ground. This is especially applicable to corrugated water tanks. These tanks are also manufactured to withstand earthquakes, which tend to happen often in New Zealand. Plastic also prevents light from passing through, which inhibits the growth of algae; a problem that fibreglass often encounters. As with all types of water tanks and rainwater tanks, these tanks also need to be flushed after installation to make sure there are no dirt and taste distinctions. And lastly, polyethylene tanks can be recycled at the end of their service life. You can use this type of water tank for storing water for doing your laundry, washing your car, for your garden, and a whole lot of applications.

Plastic has been fantastic for Promax, with 25 years of tank manufacturing, from water and milk transport, to firefighting and dust suppression.

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When installing underground water tanks, one of the most overlooked site conditions is groundwater. If ignored, it can cause structural damage or even complete tank failure. One critical factor to understand is hydrostatic crush pressure. What Is Hydrostatic Crush Pressure? Hydrostatic crush pressure occurs when groundwater surrounds an empty underground tank. With no water inside the tank to counteract the external force, the pressure from the groundwater can compress the tank walls, causing them to collapse inward. If your site has no groundwater risk, this isn’t a concern. But if groundwater is present - or may be seasonally present - it’s essential to plan accordingly. Key Consideration for Designers & Specifiers If groundwater is expected at the installation site, it’s recommended to: Use an underground tank certified to AS/NZS 4766:2020 Include an engineered uplift restraint system These requirements should be clearly outlined on your consented plans to ensure compliance and correct installation. How to Prevent Hydrostatic Crush There are two main ways to mitigate the risk: 1. Use a Certified Underground Tank The AS/NZS 4766:2020 standard confirms a tank can withstand constant external pressure - even when completely empty and surrounded by groundwater. Think of it like a submarine: it’s built to handle full submersion without collapsing. The Promax ENDURO Super Duty Underground Tank is New Zealand’s only tank certified to this standard. It’s engineered to withstand full-time hydrostatic pressure and submersion. 2. Install a Socked Subsoil Drain A site-specific option is to install a socked subsoil drain at low level around the tank. This system redirects groundwater away from the tank, preventing hydrostatic pressure from building up in the first place. Hydrostatic Crush vs. Tank Flotation While both are caused by rising groundwater, they have very different effects: Hydrostatic Crush: Groundwater squeezes the tank inward Flotation: Groundwater pushes the tank upward, lifting it out of the ground Flotation is usually managed using restraint systems. But not all restraints are created equal. Uplift Restraints vs. Installation Anchors Uplift Restraints Fully engineered to prevent flotation during full groundwater rise Covered by Promax PS1 certification Recommended as standard unless a geotechnical report confirms no uplift risk Installation Anchors Designed to hold the tank in place during installation only Not suitable for long-term flotation protection Not covered by PS1 and not recommended unless specifically engineered for flotation control Warning: Important: You cannot use both systems. If you're using uplift restraints, installation anchors are not required, and vice versa. Installing Tanks Under Driveways Tanks placed beneath driveways may benefit from the added weight and structural support above. In practice, these tanks have not shown flotation issues. However, as installation anchors are not PS1-certified, Promax cannot formally guarantee flotation performance under these conditions - even though they often prove sufficient in the field. Final Thoughts Groundwater is an invisible but powerful force. If there’s any chance it could impact your site, taking the right precautions can make the difference between a safe installation and a costly failure. At Promax, we take a safety-first approach. Unless a geotechnical report states otherwise, we assume groundwater may rise to ground level. Choose a tank engineered for the job - or manage the risk by draining it away. Need help specifying the right underground tank? Call us on 0800 77 66 29 or email sales@promax.co.nz to speak with our technical team.

Urban areas are increasingly covered by impermeable surfaces like concrete and asphalt, which prevent water infiltration and cause environmental and infrastructural problems. Innovative solutions, such as dual-purpose water tanks, are crucial for enhancing water management and promoting sustainability.