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How to Choose a Water Tank for Your Home or Business – New Zealand

Water is necessary for all aspects of life, from domestic to commercial and industrial. If you’re new to purchasing water tanks for rainwater harvesting and water storage you may be confused by the myriad of options available. Which do you choose? What material do you need? Do you need any additional equipment? This step-by-step guide aims to help answers those questions and more so you can easily choose the water tank that best meets your requirements for your home or business.

Rainwater harvesting is especially useful in New Zealand for a variety of applications, including garden irrigation, emergency supply, home appliance use, drinking water use, and more. By using a water tank for harvesting and/or storage, you can effectively save money on your mains water.

Commercial and industrial water tanks offer even higher capacities and flexibility thanks to a wide selection of material types and application-specific designs. This means that there are plenty of options available to you even if you have niche requirements for your business.

Just follow this step-by-step guide to more easily understand your own personal requirements and find the tank that best suits your needs.

1 – Understand Local Regulations on Tank Usage

Local councils may have specific regulations and requirements regarding the use of water tanks on domestic or commercial property. Be sure to check your own council’s guidelines and regulations before purchasing a water tank.

2 – Consider the Purpose of the Tank

Before moving forward, carefully consider the purpose the water tank will serve. Is it going to be used for rainwater harvesting and storage or purely storage? Is it for a household or commercial building? Will it be used for garden irrigation, potable water storage, home appliances, fire suppression, agriculture, or food prep? The answers to these questions will point you in the right direction concerning which tank is best suited for your purposes.

3 – Consider Special Requirements

Your situation may call for special requirements for your tank. Some of these might include the need for a “dry” or “wet” tank system (a dry system involves a downpipe running from the roof collection area to the tank directly, while a wet system involves a downpipe that runs underground, such as when the tank sits on the opposite side of a roof-to-downpipe connection).

You should also consider if you need a temporary or permanent tank solution; if temporary, then a flexitank may be preferable since it can be quickly deployed and emptied. Flexitanks can also be rolled up when empty, making them perfect for simple storage or convenient transport, Permanent tanks may be made of steel for long-term use. Steel, concrete, plastic, and flexible tanks can all be used for home or business!

4 – Determine Harvesting Capacity

If you’re looking for a tank for rainwater harvesting, you need to first establish the water capacity you can expect to capture. Generally, 1mm of rain across 1 square metre of roof area equates to 1 litre of harvested water. The following equation can be used to determine your capacity:

Annual Rainfall (in mm) x Roof Surface Area (in square metres) = Roof Catchment Capacity.

This will help you understand what size tank you will need later on in this guide.

5 – Determine Necessary Accessories/Add-Ons

Depending on your tank application, you may require specific accessories to get the most out of your tank and keep it functioning properly for its intended use.

Fire Kits

Fire kits come with a variety of easily connected valves, outlets, and attachments for your rainwater or bladder tank so firefighters can properly access your water for emergency situations. Local councils and firefighting professionals determine the size of the fittings required for their firefighting professionals to be able to connect to, and they will be able to use your water to help prevent further damages.

Spill Bunding Barriers

If you require extra protection from the damage caused by spills and leaks from your tank—especially bladder tanks—then spill bunding barriers can help contain those spills. Made with foam walls and covered in plastic, these barriers are quickly and easily deployed around your tank to capture spilled fluids. Some spill bunding barriers are adjustable to fit each tank, and most can be easily rolled up when not in use for simple storage.

Valves / Outlets

Certain valves and outlets can help you manually control the flow of water coming out of your tank. These can be especially useful for gardening applications when direct flow isn’t constantly required.

Tank Liners

Tank liners are made from quality plastic and are excellent to help prevent leaks as well as internal rust and corrosion on metal tanks. Most tank liners are easily and quickly installed in tanks and come in closed or open designs. Open liners allow for submersible pumps to be used when limited space and/or noise are issues.

Protective Coverings

If you opt for a flexitank, you may also require a protective covering. These coverings are made of tough plastic material and reduce the risk of UV rays, sharp objects and cigarette butts that may fall through open decks, oil on your deck, and pets and other animals that may cause harm to your tank. Protective coverings are not mandatory with every flexitank purchase but may be necessary depending on your particular situation and the location the tank is placed in.

Pumps

Water pumps made specifically for tanks work great for giving you complete and automatic control over the flow of water. Some pumps are of standard pumps that simply reduce overflow or direct flow, but others automatically prioritise the water in your tank over your mains until the tank is empty or a power failure occurs. These pumps allow you to route water from your tank to your home appliances, garden, or other applications automatically while offering an extra level of security and safety. Some pumps are externally installed while other pumps are submersible and can be installed internally to avoid noise issues.

First Flush Valves

First flush valves are an essential accessory when purchasing a rainwater harvesting tank; these valves generally feature a section of tubing with a ball stopper that collects the first several millimeters of rainwater from your roof to effectively prevent dirty or contaminated/bacteria-ridden water from entering your tank. These are easily installed and can make a massive difference in your water quality.

Filters / Leaf Catchers

Leaf catchers and filters are especially handy for maintaining water quality in your tank since many of these filters are able to prevent leaves, dirt, rodents, insects, and other debris from entering your tank. Some filters even offer a slight vibration feature that literally shakes off heavier leaves and debris. Usually, these leaf catchers are typically placed near the top of the downpipe below the roofline.

6 – Evaluate your Space

It’s necessary to first consider and evaluate your available space before choosing a water tank as your available space will potentially limit your options. With a wide-open area, such as with large gardens or farmland, there’s less to worry about concerning space and you can choose some of the largest tanks on the market. However, suburban, metropolitan, and industrial locations may have stricter space limitations. In these instances, you may choose a slim tank.

Other factors include whether you prefer the tank below ground or above ground. Underground water tanks can allow you to maintain your property’s aesthetic and keep above-ground space open and free for other applications, but the installation process may take longer. Having a tank underground can also prevent degradation from UV rays, thus extending the lifespan of poly tanks and flexitanks that may have otherwise been damaged over time by the sun. Placing a tank underground and below the permafrost layer can keep water from freezing and potentially damaging your tank material.

7 – Choose a Shape

The shape of your tank should be generally easy to decide upon evaluating your available space. If you wish to maximise your water capacity with your available space, you can go with a more square-shaped tank. Otherwise, a round tank should be acceptable for most applications. Slim tanks feature shapes that are easily fit into tight or narrow spaces to accommodate buildings that are close to a fence or another building but still require water storage.

8 – Choose a Size

The size tank you choose will be directly determined by your available space and the tank shape you require. Sizes range from short and squat to towering heights for industrial applications. Ultimately, the size you choose will be a result of the water capacity you require, which will similarly be impacted by your roof collection area and your location’s average yearly rainfall.

9 – Double-Check that the Shape and Size Fit the Site Location

After choosing the shape and size of your desired tank, make sure the end result will properly fit your location and that there are no questions regarding the ability to install the tank where it’s needed. Take ample measurements and follow any downpipes and other pipework to ensure the tank will be functional in the spot desired for it.

10 – Choose a Tank Material

Choosing the tank material may be one of the most crucial steps in choosing a water tank that matches your property and application. The five most common tank materials include sheet steel, stainless steel, plastic/polyethylene, concrete, and fibreglass. The material you choose will largely depend on a combination of aesthetics, the possibility of physical damage, and transportability.

Sheet Steel

Sheet steel tanks feature Aquaplate® and galvanised Colourbond® steel sheets that offer high rigidity and corrosion resistance thanks to a special zinc coating on the inside. Aquaplate® tanks will easily last for decades with proper care and maintenance and will handle corrosion better than galvanised steel tanks, though galvanised tanks will still last for years and remain reliable unless regularly exposed to corrosive liquids. The corrosion-resistant coating on the inside will be compromised should you attempt to weld the steel, meaning that the tanks could quickly become corroded and eventually prone to leaks.

Stainless Steel

Corrugated stainless-steel water tanks are the strongest and most durable on the market and offer a number of unique advantages over other tanks. These tanks are very easy to repair since the steel itself offers some corrosion resistance without a special coating; this means a repair usually only involves patchwork or using a waterproof sealant. Generally more corrosion-resistant than sheeted steel tanks, these tanks are less affordable but offer the highest level of durability and longevity. They are also more difficult to transport and are best suited for permanent installation.

Plastic / Polyethylene / Polypropylene

As the lightest type of water tank, plastic tanks or “poly” tanks are easily transported and make for budget-friendly tanks for your home or business. These tanks are more susceptible to degradation due to UV rays from the sun despite many of them being manufactured with UV-resistant coatings, so it may be most prudent to use a plastic tank in a more shaded area. These tanks are also the least resilient to physical force, so if there is the possibility of vehicles or equipment harming the tank, you may opt for a stronger tank. Flexitanks fall under plastic tanks and some are made using PVC material. If you opt for a plastic water tank, ensure your tank complies with AS/NZS4020:2002.

Concrete

Concrete tanks are best suited underground for water storage since, if they sustain damage above ground, they can be more difficult to repair compared to other tank types. Concrete tanks also come with the risk of “sweating” or allowing minute amounts of water to escape through pores, causing a powder-like residue to appear on the outer surface. Thus, it is best practice to install a plastic or rubber liner on the interior to prevent this leakage. Despite some drawbacks, concrete tanks remain highly durable and in some cases more budget-friendly option for a heavy-duty water tank. If you have space to spare under ground (more likely during the building process), then concrete tanks may be the perfect solution for you.

Fibreglass

Fibreglass water tanks provide high durability and longevity, making fibreglass tanks an excellent permanent tank choice for rainwater harvesting and water storage. These tanks are also easy to repair for fibreglass workers meaning repairs and maintenance won’t be as expensive as some other more complex or hard-to-reach tanks. The issue with fibreglass tanks is that they are generally not recyclable and can suffer from degradation over time. This means that fibreglass tanks are not rated for potable water storage use without a liner. These liners can be food-grade liners or flexible poly liners that are used in concrete tanks.

11 – Choose a Colour

The last step is to choose a colour for your desired tank! Many tanks, especially poly tanks, come in a wide selection of Colourbond® coatings so you can easily choose a tank that matches your building or property aesthetics and either blend into the property or add a pleasing accent.

Where Can I Purchase my Water Tank?

There are a wide variety of manufacturers and distributors you can go to find the best water tank for the lowest price. ANC Distribution is the leading water tank manufacturer in Australia and New Zealand and provides some of the highest quality water tanks on the market at the most affordable price possible. We offer tanks ranging from small poly, steel, and slimline tanks for domestic use to top industrial flexitanks and Bluescope® Aquaplate steel industrial tanks with Colourbond® finishes that are built to last long and maintain water purity for years without issue or complication. A host of accessories, add-ons, and more are also available to help you maintain your tank and save money in the long-term.

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