What are the different types of rainwater harvesting systems?

Posted by Callum Vallance-Poole, on May 16, 2022.

More people are becoming aware of the benefits of rainwater harvesting. It’s an eco-friendly solution that helps the local environment while also reducing water bills in homes that have meters installed. There are a variety of different types of rainwater harvesting systems available and we explain how they work, and which one could be best for your home.

What’s a rainwater harvesting system

A rainwater harvesting system collects water run off usually from the roof of a property where it is stored and used for various purposes around the home. There are a variety of different types of water harvesting systems, although garden-only setups tend to be the most popular for domestic properties.

Rainwater harvesting is growing in popularity as more homeowners look for ways to improve the sustainability of their properties. While roofs are not perfectly clean, you will find fewer contaminants than those found at ground level. Debris like stones and leaves can be removed more easily, while it is much harder to separate contaminants that are picked up by water at ground level.

What’s a garden only system?

A ‘garden only’ rainwater harvesting system does not provide potable water (water that you can drink) and instead is intended for use only in the garden to water your plants, flowers and lawn.

Compared to other, larger domestic systems, it is more compact and available at a lower price as they do not work as a backup to your mains water supply, making it ideal for anyone who has a smaller budget to work with. They can be positioned above or below the ground and are easy to install, so you don’t have to wait too long to get the system up and running.

Above ground rainwater harvesting systems can store more than 600 litres of water, with the purchase price also including the downpipe filter and pump, providing a steady flow of water into the tank. Some below garden only systems can store more than ten times this amount. Even if you are not so much of a keen gardener, you can use the water to wash down the driveway and back garden, or to clean your car, helping to lower your water bills while also helping to support the local environment.

What’s a direct system?

A direct pumped rainwater harvesting system has two different methods that can be used.

The first is submersible, which is often used in domestic environments and is very easy to install and set up. The pump is installed in an underground tank where harvested water can be pumped directly to toilets and other appliances around the home for daily usage.

The alternative is a suction system. In this setup, the pump is usually installed in utility room (or similar). This type of system is connected to the mains backup, so water does not have to be directed to a tank underground.

You’ll find that most of the rainwater harvesting systems rely on pumps to send the rainwater from the storage tanks to wherever it needs to be used. Compared to suction pumps, submersible pumps tend to be more efficient and will not experience similar limitations.

What’s an indirect system?

There are two types of indirect rainwater harvesting systems – indirect gravity systems and indirect pumped systems.

An indirect gravity system relies only on gravity to supply the outlets with water. For this to work, once the water has been harvested it is then pumped to the high-level tank (header tank) and then it can free flow. In this type of system, the pump is only used to fill the header tank.

Another method is the indirect pumped system which doesn’t rely on gravity to supply water to the outlets. Harvested rainwater is instead pumped to a tank that can be installed at any level, with an additional booster pump used to keep the water pressurised. This offers more flexibility as the booster pumps can be used to adjust the pressure and flow requirements of the building.

Other types of water harvesting systems

There are some other types of water harvesting systems, including:

Retention ponds

A retention water harvesting system looks just like a real pond. However, they are not naturally occurring, but instead created for specific locations to support stormwater management strategies, collecting surface water run-off from nearby pathways and roads.

Gravity only

This type of system can only be used in specific situations, as it needs to rely on a main storage tank located some distance above the water outlets, while still being below the guttering. Gravity feeds water from the gutter into the storage tank, which becomes its own header tank, before sending the water down to the point of use.

Which rainwater harvesting system is best for me?

This depends on the individual situation, as each home has different requirements. Quite often, budget plays a big role in the decision, in which case a garden only system tends to be the best solution. This is a more affordable option that also doesn’t require a complicated installation process, so the system can be in place and operational in a short space of time.

Many households also prefer not to turn rainwater into potable water, so a garden only system provides the ideal solution, enabling them to water the garden, clean the car, wash the driveway and use the water for irrigation purposes.

Will climate change affect rainwater harvesting?

Scientists have stated that rainfall levels will increase as the effects of climate change impact our daily lives. If more people are able to invest in rainwater harvesting systems, this could help reduce the risk of local flooding.

The more it rains, the faster an empty tank will fill, but this also means it is being stored rather than being discharged directly from the roof or via the guttering system into the public drains. When too much rain is sent into the sewer system at a rate it is unable to cope with, this is when floods tend to develop. The longer the periods of rainfall, the more drains struggle to cope with the amount of water being sent down into the system.

Marketing Coordinator - Based at our UK HQ in Banbury, Oxfordshire, Callum is responsible for promoting Water Management Systems, Attenuation Tanks, Treatment Plants, Rainwater Harvesting Systems and more!