8. Don’t Put a Huge Tank Somewhere Without Considering the Weight
Water is heavy.
A surprisingly important practical rule is:
1 liter of water weighs approximately 1 kilogram.
That means a 500-liter tank contains roughly 500 kg of water.
A 1,000-liter tank can contain approximately one metric ton of water—before you even add the weight of the tank itself.
That’s why you shouldn’t casually place a large water tank on a balcony, roof slab, terrace or elevated structure without making sure that the structure can safely support it.
For larger installations, structural considerations can become just as important as water regulations.
9. Don’t Let Overflow Become Your Neighbor’s Problem
This is another issue that is easy to overlook.
Imagine your tank fills completely during a heavy storm.
Where does the excess water go?
If the overflow is directed toward a neighboring property, a public walkway, a building foundation or an area that can become flooded, your rainwater system could create a new problem.
A properly designed system should have a controlled overflow route.
The goal isn’t simply to capture water.
The goal is to manage the entire flow of water safely.
Moroccan water legislation also places importance on preventing water-related risks and protecting people, property and the environment.
10. Keep Gutters and Downspouts Clean
Even an excellent tank won’t produce good-quality water if the collection system is neglected.
Before the rainy season, inspect:
- Gutters
- Downspouts
- Roof surfaces
- Filters
- Screens
- Tank covers
- Overflow pipes
- Connections
Remove leaves and accumulated debris.
A clogged gutter can cause water to overflow against walls or foundations instead of entering the storage system.
11. Think About Mosquitoes
Standing water can become a mosquito problem.
That’s why rainwater storage containers should be designed so mosquitoes cannot easily access the stored water.
Keep containers covered and use appropriate screens over openings where necessary.
This is particularly important in warm climates where mosquitoes can reproduce quickly.
12. Rainwater Is Not Always the Same
The quality of rainwater depends on many factors.
For example:
Urban environment
Air pollution and rooftop contaminants may influence water quality.
Rural environment
Dust, agricultural chemicals, animals and organic debris may affect runoff.
Coastal environment
Salt and airborne particles can sometimes contribute to contamination.
Industrial areas
Airborne pollutants and deposits may be a greater concern.
This means there is no universal rule saying:
“Rainwater is clean.”
Nor is there a universal rule saying:
“Rainwater is dirty.”
The quality depends on the collection environment and what happens between the sky and the storage tank.
13. What About Watering Plants?
This is one of the most common uses for harvested rainwater.
For many home gardeners, rainwater is particularly attractive because it provides an alternative water source for irrigation.
But even for plants, common sense matters.
Avoid collecting runoff that has been contaminated by substances such as chemicals, oils or other pollutants.
If you grow edible crops, consider how the water is collected and applied.
For example, keeping collection surfaces clean and avoiding contaminated runoff is much better than simply placing an open container beneath any available drainage outlet.
14. Don’t Store Water Forever
A storage tank isn’t a magic box that keeps water perfect indefinitely.
Stored water can accumulate sediment and organic material over time.
A good maintenance routine can include:
- Inspecting the tank regularly.
- Removing accumulated sediment when necessary.
- Cleaning filters and screens.
- Checking for leaks.
- Inspecting the lid and openings.
- Checking the overflow system.
- Looking for signs of algae or insect activity.
- Keeping surrounding vegetation under control.
The exact maintenance schedule depends on the system, climate and intended use.
15. Your Local Building Rules May Matter Too
Here’s another point that social-media posts often ignore.
Even when rainwater collection itself is permitted, the installation may still be subject to other rules.
For example, installing a large tank could involve:
- Building regulations
- Property-owner requirements
- Condominium rules
- Planning restrictions
- Structural requirements
- Plumbing regulations
- Safety requirements
This distinction is important.
The question isn’t always:
“Is collecting rainwater legal?”
It can instead be:
“Is this particular rainwater installation permitted on this particular property?”
Those are two different questions.
16. What If You Live in an Apartment Building?
This becomes especially important in a condominium or shared residential building.
If you live in a detached house and collect water from your own roof, the situation is relatively straightforward.
But if the roof is a common part of a condominium building, you shouldn’t automatically assume that you can install a large collection system there for your private use.
The roof, drainage system, terrace or other areas may be subject to co-ownership rules.
In that situation, you may need to consider:
- Who owns the roof?
- Who controls the drainage system?
- Where will the tank be placed?
- Will the installation affect other residents?
- Who is responsible for maintenance?
- Could the tank damage a common structure?
- Does the building’s copropriété regulation address installations on common areas?
The fact that Moroccan law recognizes the right to use rainwater falling on one’s property does not automatically answer every question concerning a shared building or common property installation. The property and building rules can still matter.
17. The Biggest Myth: “It’s Just Rainwater”
This is exactly where the image gets interesting.
The argument sounds logical:
“It’s just rain. It falls from the sky. How could collecting it be wrong?”
But the legal and practical issue isn’t necessarily the rain itself.
The issue can be what you’re doing with it and how you’re doing it.
There is a difference between:
Collecting a small amount of rainwater in a barrel to water flowers
and
Constructing a large storage installation connected to a building’s plumbing system.
There can also be a difference between:
Using water for ornamental plants
and
Using it as drinking water.
And there can be a difference between:
A private house
and
A multi-owner apartment building.
18. A Simple Rainwater-Harvesting Setup
For someone interested primarily in gardening, a basic system can be surprisingly simple.
Step 1: Choose the collection area
A roof is usually the most obvious collection surface.
Step 2: Inspect the roof and gutters
Remove accumulated debris before rainfall.
Step 3: Install a suitable filter or screen
This helps prevent leaves and larger debris from entering the storage tank.
Step 4: Consider first-flush diversion
This can help keep the initial dirty runoff out of the main tank.
Step 5: Use a covered storage container
Choose a container designed for water storage and appropriate for the intended use.
Step 6: Create a safe overflow
Make sure excess water can leave the system without causing flooding or property damage.
Step 7: Keep the system maintained
Clean the collection system and inspect the tank regularly.
Step 8: Use the water appropriately
For a simple garden system, non-potable irrigation is one of the easiest applications.
19. How Much Rainwater Can You Actually Collect?
This is where rainwater harvesting becomes fascinating.
A rough calculation is:
Collected water ≈ rainfall × collection area × runoff efficiency
For example, suppose:
- Roof area = 100 m²
- Rainfall = 20 mm
- Runoff efficiency = approximately 80%
A 20 mm rainfall corresponds to roughly 20 liters per square meter.
So:
100 × 20 × 0.80 = approximately 1,600 liters
from that rainfall event.
Of course, real-world results vary because of roof characteristics, evaporation, losses, filtration and the efficiency of the collection system.
This is why even relatively modest rainfall can potentially produce a surprising amount of water from a large roof.
20. Why Rainwater Harvesting Makes Sense in Dry Regions
Water conservation is increasingly important in many parts of the world.
Morocco’s water legislation itself emphasizes rational and sustainable management of water resources, and the country’s legal framework specifically addresses the collection and use of rainwater.
Agricultural guidance in Morocco also recognizes rainwater harvesting as a water-management technique.
The goal isn’t necessarily to replace the entire water supply of a household.
Even a relatively small system can reduce the amount of treated water used for tasks that don’t require drinking-quality water.
The Bottom Line
The idea that “collecting rainwater is illegal” is far too simplistic.
The actual rules depend on where you live, what you’re installing, where you’re installing it, how much water you’re storing, and how you intend to use it.
For Morocco specifically, the picture is quite clear on the basic point: Article 62 of Law 36-15 recognizes the right of owners, lawful occupants and operators to collect, store and use rainwater that falls on their properties. At the same time, the law provides that technical conditions for collection and storage systems, along with rules and quality standards according to use, are established through regulations.
So before buying two enormous barrels and connecting them to every downspout, don’t simply ask:
“Is rainwater collection legal?”
Ask the better questions:
Where is the water coming from?
Where will I store it?
Is the property private or shared?
How large is the system?
How will overflow be handled?
Will the water remain separate from drinking-water plumbing?
What will I use it for?
And most importantly:
What do the rules in my particular location say?
Rain may fall freely from the sky, but once you start building a system to capture, store and distribute it, the details matter.
For a simple garden system, the safest approach is usually to keep it modest, covered, properly maintained, physically safe, separated from potable plumbing, and used only for appropriate non-potable purposes unless the water has been properly treated and tested.
This article is general information, not legal advice. Regulations can change, and local building, condominium, health, plumbing or municipal requirements may apply in addition to water law.
