Buying the right tank for your property is a big decision with a lot of factors so it’s important to check out all the options available. There is no definitive answer as to whether plastic or concrete tanks are better, it usually depends on how you use the tanks and where they are installed. So what's the best option for your property?

All tanks need a well prepared foundation to sit on. A standard plastic water tank will weigh more than 25-30 tonnes when full. There are regulations in NZ as to how the tanks need to be installed and which building consents apply - check with your local council. 

Another factor to consider when planning your tank site is where water will go if you get leaks/overflows. Tanks are often installed on hills with a gravity pumping system so that you are still able to access water if pumps fail or there is a power cut.

Plastic tanks are often cheaper to buy and install compared to concrete tanks. They are maneuverable and lightweight so easy to transport and position. Most modern tanks are UV stabilised and made of food grade polythene for household drinking water. It is usually easier to fit outlets to and change lines on plastic tanks.

The flexibility of plastic tanks also allows for some movement in earthquakes, preventing damage. They can however be easily damaged by fire and sharp objects. Another risk to plastic tanks is getting pierced or warped by tree roots growing around the tank. 

Plastic tanks have widely been used for more than 50 years and are becoming more common than concrete ones. They can be recycled after use, however, they cannot be made from recycled plastics due to food quality standards in New Zealand. 

Concrete tanks are much stronger and more durable than plastic. They can be buried underground for landscaping and can withstand fire, however are often damaged by earthquakes in high risk zones. 

New Zealand rainwater is slightly acidic. Storing rainwater in a concrete tank raises the pH of the water due to lime leaching into the water, balancing out the acidity. Acidic water can damage plumbing hardware and cause green copper staining on household fittings. Concrete tanks will also keep the water cooler in the hot summer months. 

Installing concrete tanks requires a lot more preparation and heavy machinery. The site must be accessible by a hiab or else the tank will need to be built on site. This makes installing new concrete tanks a very expensive project. 

Concrete tanks can last for decades, however, once they start to deteriorate, there can be a lot of issues that aren't so easy to fix. This is particularly problematic with septic and wastewater tanks. The standard for concrete tanks allows some leakage of stored water however plastic tanks are (usually) completely watertight. 

All tanks will last longer with proper maintenance. Frequent cleaning and water quality testing is important for the longevity of the tanks. Regular repairs and maintenance to fix small damages will prevent bigger problems down the line. 

There is no hard and fast rule as to which kind of tank is ‘better’, it all depends on your property and your needs. Weighing up the pros and cons of each type of tank is the best way to start.