What is the best colour for a water tank?

The best colour for a water tank in New Zealand is typically a lighter, UV-resistant colour such as beige or light green because they stay cooler, reduce algae risk, and last longer in NZ’s high-UV climate. However, the ideal colour also depends on your location, purpose, and aesthetic preferences.

Many people in New Zealand are choosing to install a water tank at home for environmental and financial reasons. If you are wondering about the best water tank colour or whether the colour of your poly water tank matters, this guide will help you understand your options.

If you are considering whether to install a water tank, one of the questions you will inevitably face is what colour of tank is best, especially when comparing types such as concrete, stainless steel, or polyethylene (PE) water tanks.

PE or "poly" water tanks (often called plastic water tanks) are the most popular option in NZ because they are:

Lightweight
Easy to install
Non-corrosive
Long-lasting
Recyclable
Seamless (lower risk of leaks)

Poly tanks can also be produced in a wide range of colours, which is why many homeowners wonder: Does water tank colour matter?

Does the colour of my water tanks matter?

There are a few conflicting schools of thought when it comes to the best colour for poly water tanks. Some say that darker water tanks are better because they help to prevent the growth of algae. Algae thrive in sunlight so the more light that the water in your tank is exposed to, the more chance you have of developing algae.

This, however, doesn’t mean that lighter-coloured water tanks are a breeding ground for algae. Most light-coloured water tanks are opaque and manufactured with an adequately thick wall to prevent algae from forming.

Other sources suggest that darker tanks actually provide a better breeding ground for algae and bacteria. This is because they absorb more heat from the sun that lighter coloured tanks and warm water is conducive to bacteria and algae growth.

Today, all polyethylene (PE) water tanks in New Zealand are UV-stabilised and engineered to minimise algae growth, even under strong NZ climate UV conditions. Most people today, instead, pick the colour of their water tank for aesthetic reasons, to match the environment in which it will be installed.

Dark vs Light Water Tanks (Pros & Cons)

When choosing the best water tank colour, many homeowners wonder whether a dark or light tank is better. Both options have advantages, depending on your location, intended use, and preferences. Here’s a simple breakdown of the pros and cons of each type to help you decide.

Dark-Coloured Tanks (Black, Dark Green, Charcoal, Dark Grey)

Pros

Better at blocking sunlight, which helps prevent algae growth
Provide stronger UV resistance in high-UV regions like New Zealand
Fade less noticeably over time
Blend well with natural surroundings such as bush, fencing, or rural landscapes

Cons

Absorb more heat, which can warm stored water during summer
May not suit all modern or light-coloured home designs
Can slightly increase internal tank temperature, which may contribute to bacteria growth if the tank is in full sun

Light-Coloured Tanks (Beige, Mist Green, Light Olive, Light Grey)

Pros

Stay cooler in direct sunlight, helping maintain lower water temperatures
Often have a longer lifespan in NZ’s strong UV climate
Fit a wide range of architectural styles and look more neutral over time
A good option if the tank is installed in a fully exposed or north-facing area

Cons

May allow slightly more light penetration compared to darker tanks
Less effective at suppressing algae if the tank walls are thinner or have lower opacity
Can show dirt or weathering more easily, depending on the colour

Choosing a water tank on looks

Most people choose a colour that blends into the surrounding environment:

Near the house
Along a fence line
Beside a shed
Within a landscaped garden

However, houses and fences are repainted more often than tanks are replaced, so a neutral colour tends to be the safest long-term choice.

Popular neutral tank colours include:

Beige
Mist green
Light olive
Grey

If you don’t love the colour of a tank that fits your budget, you can screen it using:

Timber slat panels
Natural planting
Fence extensions
Decorative screens

Practical colour considerations for your water tank

Whilst the aesthetics of your water tank are undoubtedly important, there are some practical considerations as well.

We have discussed the differing opinions regarding the colour of your water tank and the likely breeding ground you create for bacteria and algae. This is definitely something to consider and something you should talk to your water tank supplier about.

The colour also affects the temperature of the water you are storing as well. This is especially important if you plan to use the water you collect for potable purposes (drinking, cooking, bathing etc).

A dark-coloured water tank will absorb a lot more heat from the sun than a lighter-coloured tank and during the warm summer months, this means the water in your tank is likely to be much warmer than a lighter-coloured tank.

Whilst we have discussed the potential impact on algae and bacteria of having warmer water, it is also not that refreshing to drink warm water so this is a consideration you should factor in. If you are only collecting the water for watering the garden or washing the car, this will be less of a consideration.

There has been some research conducted to suggest that lighter-coloured tanks also have a longer lifespan than darker tanks. Whilst all poly water tanks are built with UV protection, the research suggested that some colours lasted longer than others. Lighter-coloured tanks like beige or light green, for example, were found to outlast their darker compatriots such as dark green, black or blue.

This should be a consideration, especially if you plan to locate your tank in direct sunlight. If possible, we always recommend positioning your tank in a shady position or using screening to protect your tank and help to keep the water cooler.

Summary

There are both practical and aesthetic considerations to factor in when you are purchasing a water tank.

When it comes to measuring the amount of water in your tank, the colour doesn’t really matter. One of the biggest barriers for people adding a rainwater tank at home is the uncertainty of not knowing how much water is left in your tank. This applies to rainwater tanks stored both above and below ground.

At Smart Water, we have engineered the most advanced tank level indicator available that now offers full cloud connectivity.

Easy to install yourself, your Smart Water tank indicator provides you with all the information you need from our app or from one of our LCD displays. Find out how much water you consume on average from your tank, accurate pressure data and estimates on when your tank will run out of water based on current usage.

Find out more about our range of products or check out our FAQs for more information.