Rainwater harvesting: here's how to do it right

Optimise and save resources while avoiding waste

Inspirations / How to

13/09/2023

Estimated reading time 5 minutes

Does the thought of rainy days depress you? The upside is that they provide the opportunity to stock up on water that you can utilise in all sorts of ways thanks to a rainwater collection system.

Rain is a free resource that can help us to achieve water self-sufficiency. It doesn’t go on your utility bill, it prevents you wasting drinking water from the tap when it’s not needed, and it gives you autonomy from the mains supply (at least partially), especially in the event of restrictions due to droughts (such as time constraints on sprinkler usage, hosepipe bans etc.).

Tap water is a high-quality resource because it is drawn from groundwater and treated before being distributed to homes. It is intended for human consumption and using it for anything else is wasteful. For watering plants, washing the car, cleaning the driveway and so on, a less valuable but naturally available resource such as rainwater is sufficient. Even rainwater, once purified, can be used in the home for domestic purposes (flushing the toilet, washing machine and more).

Water is essential for our very survival, but it is a finite resource. Each of us can make a difference in our own small way, with responsible behavior, by use it sparingly and efficiently. Today we will find out how to prepare a DIY rainwater harvesting system to water the vegetable patch and garden.

How to create a rainwater harvesting system

Rainwater is not drinkable, but it is sufficient for watering plants, and is actually better than tap water in this regard, because it is pure (being generally free from mineral salts, dissolved gases etc.) and at ambient temperature (being stored in an outdoor container). Excess salts—particularly chlorine and calcium, which are present in tap water—are not healthy for plants. It’s important that the water is at the right temperature, so not too cold but similar to the soil temperature, especially in summer. This is so that plants don’t suffer thermal shock.

The basic components of a rainwater harvesting system are:

  • Catchment area

  • Transport system

  • Storage tank

  • Distribution system

The catchment area is where water collects in the form of rain, snow, etc.: the roof of the house or garage lends itself perfectly to this purpose. The amount of water collected depends on the average annual rainfall in your area, as well as on the size, shape and material of the roof itself.

The transport system conveys the water from the catchment area to the tank, where it is stored. For this purpose, it make sense to utilise existing gutters and drainpipes. Before the water reaches the tank you can filter it to remove leaves, branch fragments etc. that it picks up along its path. Once deposited in the storage tank, the water settles, which enables even the finest impurities to deposit at the bottom of the tank.

On the market you can find robust outdoor rainwater butts, which are generally made of polyethylene. They come in different shapes: the most common are rigid barrel-shaped, cubic and cylindrical ones, but there are also foldable containers that you can assemble and disassemble as needed. Choose the tank capacity based on rainfall, catchment area and water requirement. The water requirement of your vegetable plot and garden depend on the climate, weather pattern, type of soil, the plants you grow and the area that needs irrigating. When choosing a tank to collect water for irrigation, also take into account the space you have available. It should preferably be placed in a sheltered and inconspicuous spot.

In order for the rainwater to pass down the drainpipe into the tank, you can purchase a rainwater collector or a special connection kit. The rainwater collector is usually a metal tube applied to the drainpipe. It incorporates a leaf filter and a hatch which, once opened, acts as a channel that diverts the flow of water into the tank. The connection kit, which is generally made of plastic, comprises a fitting that you attach to the drainpipe (equipped with a filter and an overflow drain) and a manifold that connects to the tank at the other end.

A rainwater butt or tank is equipped with at least one tap, which can be used to fill a watering can or connect to a hosepipe. The tank should be raised off the ground so that sufficient gravitational pressure is built up to force the stored water down through the tap and along the hosepipe. You can build a solid dry base (without mortar) using concrete blocks or bricks.

To make a simple drip irrigation distribution system, lay an irrigation hose on the ground between your plants, connect it to the tank, close it with an end cap at the opposite end, and puncture it along the section that runs alongside the plants. If the gravitational pressure is insufficient to transport the water beyond a certain distance, you can use a water pump. If, instead of water, you need to transport heavy and bulky equipment over long distances, then a transporter can do the job effortlessly.

With a water pump you don't need a rainwater butt for irrigation, because you can draw water directly from a stream or irrigation canal. You can find all the details for setting up a water pump in this article on how to water the vegetable patch.

In addition to harvesting rainwater

Using water resources prudently means using it more efficiently on the one hand, and saving it and avoiding waste on the other. In addition to installing a rainwater harvesting and collection system for the benefit of your vegetable plot and garden, you can adopt various tactics to cultivate produce with minimal water usage. One way is to work the soil thoroughly—using hand tools or a rotary tiller – before seeding and planting. When water is scarce, here's what else you can do to protect your vegetable patch from the heat.

A water pump is useful not only for irrigation, but also for transporting water from one point to another, for example when you need to empty and refill a swimming pool or pond. In both cases you can use rainwater which, particularly in the case of swimming pools, must first be purified with special filtering systems. Furthermore, with a water pump you can drain soil, holes, flooding, etc. (here is how to use a water pump with dirty water).

Collecting and reusing rainwater for watering your vegetable plot and for other domestic and non-domestic uses, is one way to become self-sufficient. Another way is to grow your own food, in which maximising the productivity of your vegetable patch plays a central role.

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