Rainwater Harvesting – How to Collect Rainwater

In the modern ecological world, learning how to collect rainwater should be near the top of your to do list.

Besides being very practical and environmentally friendly, it is also a cost efficient alternative to using the mains water from your local supplier.

Indeed, rainwater harvesting is becoming more popular as many households and businesses reduce their demands on water by opting for this cost-effective alternative.

If you’ve never considered rainwater harvesting, then you should read on to learn more about the benefits and give it serious thought.

What is Rainwater Harvesting?

Rainwater Harvesting Illustration

Rainwater harvesting refers to the process of collecting run-off water from building structures such as roofs into tanks for later use.

The aim is to put it to good use, rather than allowing it to go into the sewage system or a soak away in the ground.

Typically, rainwater collects in gutters which is then channeled into downpipes straight back into the sewage system or a soakaway.

Rainwater harvesting however takes that water and redirects it straight into storage tanks with an in-built filtration and pumping system for later reuse.

In some countries, rainwater collection has become very popular.

Consequently, there’s now a variety of rainwater harvesting systems that you can choose from to suit your own personal preferences.

Why Collect & Store Rainwater?

Glass of Water

There are numerous benefits to collecting and storing rainwater.

First of all, it’s essentially a free source of water, so you’ll be making significant savings on your utility bills.

Rainwater can be used for various things as it is relatively clean and free from chlorine.

It’s an environmentally friendly option which promotes the conservation of water as well as self-sufficiency.

In fact, many households are using rainwater harvesting, particularly in places where there are controls on the water supply or water restrictions are in place.

Harvesting rainwater is also a great way to reduce stormwater runoff.

Moreover, drainage problems can be reduced particularly in wet areas.

Some households use the rainwater collected as their main source of water, whilst others may use it as a back up source of water; perfect in case of emergencies.

Best of all, rainwater harvesting doesn’t require a considerable investment to set up.

Relatively simple technologies and systems that are flexible and modular can be used to put everything in place.

Rainwater collection systems are also easy to maintain.

So living off grid is a lot more achievable than you may have first thought.

Importance of Rainwater Harvesting

Desert Drought

Rainwater harvesting offers a variety of advantages.

Besides focusing on the direct benefits as a household or a business, it’s also important to appreciate the important role such systems plays.

Water is an invaluable resource, yet in the western world, it is something we take for granted.

With the onset of climate change and rising demands, water supplies could be limited.

With rainwater harvesting, you reduce your own personal demands on the ecosystem and become more self-sufficient by essentially harvesting a free source of clean water.

The water collected can be used for several different things, as well as stored as a backup.

Therefore, installing a rainwater harvesting system is a great option not only from a cost perspective, but also as a way to reduce your environmental footprint, making your home more ecological.

Uses of Collected Rainwater

Garden Sprinkler

The collected rainwater can be used in practically the same way you would use tap water.

By installing a pump and filtration system, it can be fed back for any type of indoor use in your home, as well as for irrigating your garden.

You could easily connect it to a sprinkler system to maintain your lawn, flowers or vegetable patch.

Or it could be used to refill your pond or water features in the garden.

You could even use it to clean the car or hose the pets!

The collected rainwater can also be used as an alternative to tapwater to pressure-wash driveways, yards and pavements.

Inside the home, the collected rainwater can be used for any common fixtures, such as the toilets, basins and even the washing machine!

Some households even go a step further.

By fitting a suitable filtration system, the water can be drinkable just like tap water!

How to Collect Rainwater

Nowadays, there’s a wide range of different rainwater harvesting systems available.

We shall go into more detail about each one below, so you can decide your preferred route on how to collect rainwater.

It’s important to understand the differences between them to ensure you’re well informed about the best option for your personal demands.

Water Butts & Barrels

Water Butt

This is the most basic form of rainwater harvesting.

The traditional garden water butt or barrel is a container that collects rainwater via the drain pipes along with any natural rainfall.

The collected water is usually only used to water plants and trees in the garden.

If the water butt is paired up with a rainwater filter, the quality of the water will be further improved.

This is a system that’s very easy to install.

You will be able to find water butts in most garden centres and DIY stores, and there is no need to worry about anything much else.

Water butts can fit into most gardens directly beneath the guttering, so there shouldn’t be any space concerns.

That said, you will need to bear in mind that water butt capacity is limited to around 50 to 100 gallons.

So it’s important to keep track of the water level in the barrel to avoid the possibility of overflowing and flooding your patio or garden area.

Water butts are also prone to freezing during colder winter months, which can lead to cracking and splitting of the shell, rendering them useless.

So choose how to collect rainwater carefully.

Rainwater Tanks

Water Tanks

Rainwater tanks come in a variety sizes as well as materials.

There are polyethylene tanks, galvanised metal tanks, slimline cisterns, and underground cisterns to name a few.

It’s important to choose the most suitable rainwater tank for your particular demands.

During rainfall, water is collected from the roof down the gutters to the rainwater storage tank where it is filtered.

It is critical to choose a tank of the right size to ensure that it is as effective as possible.

Get a tank that is too small and it will not be able to keep up with demands.

Install a tank that’s too large and it may end up being an unnecessarily expensive investment.

Direct-Pumped (Submersible)

Submersible Pump System

This is a very common option, whereby a submersible pump is placed in the underground tank.

The harvested water is pumped directly into toilets and appliances that use water.

Sometimes the system is improved by allowing for a small amount of mains water to be fed in, in order to make sure there’s always an adequate supply of water.

In commercial settings, a dual pump arrangement is usually used for more peace of mind.

Direct-Pumped (Suction)

In this case, the pump is not located within the tank, but inside a control unit.

This is usually installed somewhere in the house, such as a utility room.

This control unit is essentially responsible for the backup of the mains water supply.

So there will be no need for mains water to be sent to the tank.

Indirect Gravity

In this system, the harvested rainwater is pumped to a header tank.

Then, it supplies the outlets by means of gravity, hence the name of the system.

In this case, the pump will only work in situations when the header tank requires refilling.

Mains water is fed directly to the header tank, instead of the main harvesting tank.

Indirect Pumped

This is very similar to an indirect gravity system.

However in this case, the internal tank is installed at any level of the building because there’s no reliance on gravity to influence water pressure.

In this system, there is a booster pump set which pressurises the water supply.

This system is slightly better since there’s no need to feed mains water to the underground tank.

Moreover, there is more flexibility since the booster pump can be set to the required flow or pressure needs of the dwelling.

Gravity Only

Rainfall Gutters

In some cases, a rainwater collection system that relies only on gravity can be installed.

In such a case there will be no need for a pumping system to increase pressure.

In this type of system, the rainwater is collected from the building’s roof, where the gutters are situated directly above the filter and collection tank.

The tank and filters are subsequently located above all of the outlets and plumbing feeds.

Hence this rainwater collection set up is only possible if the storage tank is placed below the level of the gutters, but higher than the outlets where water is supplied.

This system completely relies on the power of gravity to sufficiently feed the collected and filtered rainwater to different parts of the building.

Which System Is Best For You?

As noted previously, every system has its respective plusses and minuses.

So there might be more than one option that could work well for you.

There are various factors to consider before making your choice on how to collect rainwater.

For instance, if internal space is somewhat limited, it may not be feasible or even possible to fit a header tank.

In such cases, a direct pumped system may be most suitable.

In fact this kind of system is usually the most common choice in households.

On the other hand, if it is possible to install a high level header tank, the indirect gravity option is a very good choice.

This is even more so if there is no need for the system to supply water at high pressure.

In cases where high pressure is needed, then it is best to opt for an indirect pumped system.

This is also a more feasible option in the case of relatively large buildings.


In this day and age where we are all too aware of the importance of considering our environment.

It’s a very good idea to reduce your mains water usage by learning how to collect rainwater by setting up your own system.

There’s different options available and it’s neither costly nor difficult to set up such a rainwater collection system.

And you could reduce your mains water usage by up to 50%!