What you need to consider before deciding on a rainwater tank installation

There are a range of benefits to installing a rainwater harvesting system for your house and property, including keeping your gardens looking healthy in times of low rainfall and reducing your water bills. To ensure you select a rainwater harvesting system that is just right for you, you should firstly consider how you plan to use the rainwater you collect, how much you are capable of capturing, where the best place to install the tank is and what type of pump you need.

How am I going to use the rainwater? How much do I need to collect?

When it comes to investing in a rainwater harvesting system, it is important to think about how you plan to use the water you collect. Rainwater cannot only be used to keep your grass green and flowers flourishing, but also used to supplement mains water supply inside the house, particularly for toilet flushing and laundry use.

If you plan to use your rainwater for gardening only, some advisors recommend 1,000 litres or less for a townhouse, at least 3,000 litres for a small garden, and 5,000 litres for a larger garden.  As a guide, running your hose at maximum capacity can use up to 20 litres per minute, so a full 1,000 litre tank will only provide around 50 minutes of hosing.

It’s also important to consider the size of your rainwater catchment area - generally your roof area. As a guide, 1 mm of rain over 1 m² of roof area will equate to 1 litre of rainwater entering your tank.  Also make sure you consider the average rainfall in your region.

Where am I going to put the tank?

Firstly, check whether there are any local council regulations about where you may put your tank. For example, in some areas there is a minimum distance from the side property boundary. When considering where to put your tank, try and select a position that will collect water from the largest possible roof area.  Also remember that you will need the top of the tank to be lower than the gutter on your roof. If possible, find a location where you can connect more than one downpipe to your tank. Make sure the tank won’t restrict access to the garden or block views and is aesthetically acceptable (also try and consider your neighbours’ perspective as well). 

Next, you will need a base for the tank, which needs to be slightly larger than the tank diameter. You can build this yourself or have your installer do it for you. A sturdy solution for a base is a reinforced 100 mm concrete slab. The slab can be square or round and should always be at least 10 cm larger than the diameter of the tank. A timber frame filled with crusher dust or concrete, to prevent subsidence could also be used. This is important, because if the tank is not level, the weight of the water will make it lean to the side and become unstable. Before building your base it is recommended you check your local council regulations to ensure building approvals are not required.

How do I choose the right pump?

To utilise your harvested rainwater to its full potential or to connect an irrigation system, or even a hose, you will need a pump. There are a range of rainwater pump options on the market and to help you decide what is right for you we have listed some helpful hints that you can check out in our article PUMP PERFECT.

We are your local pump experts and an Authorised Grundfos Dealer. Grundfos pumps are market leaders, committed to providing new and innovative products that take comfort and simplicity to the next level, and for these reasons, we sell and recommend the new SCALA2 domestic pump.