Disconnect your roof: Be part of the solution

Do you live in Brussels with a terrace or a garden and want to install a rainwater harvesting tank or a rain garden to protect waterways?

Sign up now to be among the potential candidates for the free installation of a rainwater tank (with or without a swale)!

In cities, rainwater is usually directed towards the sewers. During heavy rainfall, the sewers cannot manage the volumes of water, and thus this mixed water (rainwater and wastewater) flows into Brussels’ waterways, such as the Senne and the Canal. This is the main cause of poor water quality in Brussels (read more about the issue of storm overflows in Brussels here).

It is high time to consider rainwater as a resource that can be used for various purposes in our daily lives. Installing a rainwater tank allows us to utilize this resource, and if we connect this tank to a garden, it also helps reduce the volume of rainwater going into the sewers, thus reducing sewer overflows (also known as storm overflows) into waterways.

In practical terms, the city needs to disconnect a significant area from the sewers to reduce the number of storm overflows to zero. This must be done by public authorities and large companies, by disconnecting streets, squares, company roofs, and public buildings. But also by disconnecting the roofs of houses and private apartments. Waterways need you. You can help achieve cleaner and more nature-filled waterways by disconnecting your roof, whether you live in an apartment with a terrace or in a house with a garden.

What can rainwater be used for at home?

To water plants, clean the terrace, and wash your bike

Rainwater has low mineral content, is low in chlorine and fluoride, and has a slightly acidic pH, which promotes flowering and plant growth. For many daily tasks such as cleaning the terrace or cleaning your bike, rainwater is perfectly usable.

To flush the toilet

We use approximately 36 liters of drinking water per person per day for toilets. However, it is not necessary to use high-quality drinking water to flush the toilet. Therefore, it is perfectly possible to replace this water with rainwater.

To wash clothes in the washing machine

The valorization of rainwater for laundry washing presents numerous advantages. Indeed, rainwater is softer, hence better for clothes and pipelines. Moreover, it also allows for significant savings on water consumption.

3 good reasons to use rainwater


Contribute to fighting against floods and storm overflows

During heavy rains or prolonged rainy periods, rainwater tanks store a portion of the water. Additionally, if the overflow from this tank is directed into a rain garden, this rainwater will no longer go into the sewers. By disconnecting your roof, the amount of rainwater flowing into the sewers decreases, thereby reducing the number of sewer overflows and the risk of flooding.


Reduce the amount of your water bill

A family of 4 pays an average of 550€ per year for water (110m³). For a couple, the bill amounts to about 375€ (average consumption of 75m³). With moderate use of rainwater (for toilets, household chores, and the garden), this annual bill can be reduced by one-third to one-half.

Preserve water resources

It does rain often in Belgium, that’s true, but we still experience episodes of drought, where the groundwater level is particularly low. And generally speaking, it’s important to preserve water resources.

We disconnect your roof for free for you

A rainwater tank on your terrace


We come to install a 276L rainwater tank, like the one you see in the photo above, at your place.

Sign up if you own an apartment/house with a terrace or garden and want to reuse your rainwater. You just need a visible downspout and enough space around to place a tank to take the step towards disconnection!

A swale in your garden


We will also install rainwater tanks connected to a swale in the garden so that the water infiltrates into the soil. This will be done in collaboration with Ferme Nos Pilifs. This action is only available for houses located in Laeken thanks to the grants from the City of Brussels.

Sign up if you own a house with a garden in Laeken and want to reuse your rainwater and infiltrate it into your garden.

This campagne is made possible thanks to the financial support from Brussels Environment, the City of Brussels, VGC, WWF, and Brussels Mobility.

Not among the candidates? Install a tank yourself!

We may not be able to respond to all your requests, but below you will find all the necessary information to install an outdoor rainwater tank yourself. There are several types of tanks, and there are also regional and municipal grants available to assist you.

The different rainwater harvesting systems

A rainwater tank on the terrace

An outdoor rainwater tank of a few hundred liters can easily be installed on a terrace. This system can be used to water plants, clean the terrace, wash your bike, etc.

For whom: This type of tank can be installed on an apartment or garden terrace. You just need to find the rainwater pipe and have enough space around to place the barrel.
Budget: ~ €200 to €500
Grants: City of Brussels, Jette, Saint-Gilles, and Watermael-Boitsfort (see details below).
Some examples of tank models:

Connect your rainwatertank to your garden

A rainwater tank fills up quickly, especially during heavy rain events. When it rains a lot and the tank is full, the rainwater will still be directed to the sewers. Unless the overflow of the tank is connected to the garden. In this case, when the tank is full, the excess water goes to a swale or a rain garden.

A swale is a depression in the ground used for collecting, retaining, conveying, draining, and/or infiltrating rainwater runoff from impermeable surfaces. mostly shallow, temporarily submersible, with gently sloping banks, the swale is typically vegetated to enhance water infiltration (Sustainable Building Guide).

This solution helps to limit the volume of rainwater in the sewers, thereby reducing the risks of flooding and stormwater overflows into the canal and the Senne river.

  • For whom: Connecting your tank to a swale can be done by homeowners of a house or an apartment with a garden.
  • Budget : 100 – 2000 € (if you do it yourself this can be very cheap)
  • Grant : only at the city of Brussels and the municipality of Jette.

An underground rainwatertank

To connect your toilets or washing machine to a rainwater system, it is preferable to choose a larger underground tank. This option requires more extensive construction work, which is why we will not cover this topic in detail in this article.

There are many grants available for this type of tank (see below).

  • For whom: A tank can be installed during construction work under the house, the terrace, or in the garden.
  • Grants: Regional and municipal grants are available in most municipalities.

Grants to help you out

In the Brussels region, there is a regional Rénolution grant as well as various municipal grants. The amount varies depending on the municipality and it can go up to €1700. This is a significant incentive to start collecting rainwater and installing an outdoor or underground rainwater tank.

Regional grants

Outdoor Rainwater tank: /
Underground rainwater tank: The Brussels Region offers a financial incentive through the Renolution program for rainwater tanks (minimum 1000L connected to a toilet or washing machine), ranging from €500 to €1100 depending on income levels.

More information: https://renolution.brussels/fr/aidesfinancieres/c3-gros-oeuvre-et-gestion-de-leau-recuperation-deau-de-pluie

Municipal grants

Outdoor rainwater tank: /

Underground rainwater tank: up to 250 €
Condition: min 2000L, connected to a toilet or a washing machine.
Website: https://1082berchem.brussels/wp-content/uploads/2015/11/Prime-syst%C3%A8me-de-citerne-de-collecte-deau-de-pluie.pdf 

Outdoor rainwater tank: up to 100 €
Conditions: Between 150L and 500L
Website : https://www.bruxelles.be/prime-tonneau-recuperateur-eau-de-pluie

Installation of a system for infiltration in the ground: up to 500 €
Website : https://www.bruxelles.be/prime-systeme-infiltration-eaux

Underground rainwater tank: up to 1000 €
Conditions: min 2000L, connected to a toilet.
Website : https://www.bruxelles.be/prime-citerne-eau-de-pluie

Soil permeabilization: up to 1000 €
Website: https://www.bruxelles.be/prime-permeabilisation-sols

Outdoor rainwater tank: /

Underground rainwater tank: up to 500€
Conditions: min 1500L, min 40 m² disconnected roof area, connected to a toilet or a washing machine.
Website : https://www.ixelles.be/site/802-Prime-relative-aux-systemes-de-recuperation-d-eau-de-pluie

Outdoor and underground rainwater tank: up to 300  €
Conditions: Any element intended for rainwater harvesting.
Website: https://www.jette.irisnet.be/fr/pdf/primes-2024/reglement-formulaire-recolteur-deau-de-pluie-1.pdf

Collecting rainwater in the garden: up to 400 €
Conditions : Any open-air structure allowing water infiltration to a depth of less than one meter (swale, ditch, infiltration trench, dry basin, etc.).
Website : https://www.jette.irisnet.be/fr/pdf/construire-et-renover/prime-eau-pluviale-reglement-def.pdf

Outdoor rainwater tank: /

Underground rainwater tank: up to 500 €
Conditions: min 2000L, min 40 m² roof area disconnected, connected to a toilet or a washing machine.
Website: https://www.molenbeek.irisnet.be/fr/fichiers/reglements-communaux/prime-recuperation-eau-de-pluie/reglement-prime-citernes-eau-de.pdf

Outdoor rainwater tank: /

Underground rainwater tank: up to 1700€
Conditions: min 1000L, connected to a toilet or a washing machine.
Website: https://sjtn.brussels/sites/default/files/documents/2022_10_20_primes_communales_reglement.pdf

Outdoor rainwater tank: /

Underground rainwater tank: up to 500 €
Conditions: min 2000L
Website : https://www.uccle.be/sites/default/files/filemanager/Reg-Charte/ENVI_Reglement_CIEP_REGL_2012_U1180_fr.pdf

Outdoor rainwater tank: up to 100 €
Conditions: a rainwater tank for reuse
Website: https://www.watermael-boitsfort.be/fr/vivre-a-watermael-boitsfort/environnement/primes/eau-de-pluie

Underground rainwater tank: /

Outdoor rainwater tank: /

Underground rainwater tank: up to 500 €
Conditions: min 2000L, minimum 49 m² disconnected roof area, connected to a toilet or a washing machine.
Website: https://www.woluwe1200.be/primes-vertes-octroyees-par-la-commune/

Do you want a tank or a swale? Sign up with this form!