Harvesting rainwater for drinking

Rainwater useful and safe to drink

Since I was a child, I often heard that drinking rainwater was impossible, or unhealthy, because it was like distilled, containing no minerals. However, since I am visiting South-East-Asian countries, I’ve seen that people actually collect and drink the rain water in many countries, such as Thailand, Cambodia, Indonesia and even Australia. Millions of people actually drink rain water.

Finding clean water to drink in South-East-Asia is sometimes a challenge (especially if you try to lower your consumption of plastic bottles). Mineral water, ozonated water, reverse osmosis, ultraviolet (UV) treatment and different filter system or treatments are used, either by companies selling small bottles, by local cleaning water services and companies, as well as the water refill machines found in the street in small and big towns. But, going to the countryside, where no city nor big facilities are seen, you can wonder where people get they get their drinking water from. This is when you will notice some huge jars containers under the houses’ roof, they are made of cement and where made in clay in the past. I drank this water when I stayed at a friend’s house in a small country side village in Issan (North-East of Thailand), the water tasted fine, even nicer than some bottles, and I had no health problem (staying around 5 days). As a compare, I remember getting ill (over tired and stomach disorder) by drinking boiled water in Indonesia for a few days.

Rainwater harvesting is a thousands years old practice in Thailand and in the past years it has increased in popularity thanks to the use of bigger jar containers. The traditional container was more natural because it was in clay rather than in cement, but it could not store a lot of water. The Population and Community Development Association (PDA) has started a Rainwater Jar Program in order to promote rainwater collection, increasing access to clean water in the country side or remote areas. This project, that involves trainings for safely collecting water and jars maintenance, is also bringing new incomes to locals who make these jars. This initiative was then supported by Thai government and private donation, which has led to the manufacturing of billions of jars at an affordable price for helping families and communities living in places that may run out of fresh water during dry season. These jars can be equipped with a lid, a faucet and a drain. I saw these kind of containers on the small island of Koh Mak, next to almost every house.

A simple and economic system

A Thai jar like this one costs around 15 USD and collects about 2’000 litres which should be enough for a family to have drinking water for the dry season. Stored like this, the water also stays at a nice temperature, even during April the hottest month of the year. Keeping water still in the jar for several months is actually safe because the pathogens should gradually die off. Nevertheless, it is important to make sure the roof and the pipe collecting the water are clean of birds dejections, algae, dust and chemicals that can be in the roof’s material or tiles. To keep the water safe from birds’ drops, it is advised to keep the jar far from trees where birds could sit.


The rainwater is harvested during the rainy season, this period of the year lasts several months and gives almost all the water rain of the year. After this wet time, there might be 4 months or more without any drop coming from the sky, of very scarce rains. So each family has to make sure to have enough containers for supplying drinking water (and maybe water for the garden) during the whole dry season. The water is collected from the roofs and redirected to the big thanks or jars. A piece of metal or a proper lid is used for covering the jars and to prevent the dirt from falling into the freshly collected water, from contamination, insects breeding, from animals coming there to drink as well as from evaporation. For preventing mosquito breeding, which can spread malaria, dengue fever and other mosquitoes related disease, it is important to carefully close the jar or other water thank with its lid. The lid can also be used for deciding which rain to catch, for example getting the second rain after a long period of dry weather, so as to make sure that the first rain would have washed away the dirt, leaves, bird drops and other from the roof collecting the water.

If rainwater is naturally drinkable, or healthy, it is now getting polluted by air pollution. You may have heard about acid rains, or other elements that can be trapped in the drops of water when raining, like black dirty smoke from industries. One of the things a Thai friend told me that locals do to check if the rainwater would be drinkable is to look at the tree leaves around them, such as the mango tree. Are the leaves looking clean or are they wearing black dirt on them? The leaves show a part what the rainwater carries with its drops.

For preventing dirt, leaves and other elements we don’t want to get in our water, different improvement can be added to any simple water collection. Using some filters to catch the leaves is the first easy thing to do. Some research is also done about growing plants on the roofs that can filter the water, just like a fresh water stream in the forest.

Other solutions consists of using or making a water filter, such as the one Jon Jandai (see under) promotes with rocks, sand and home made active charcoal. This kind of filters can be used either to filter the rain water or to filter the city water (that can contain bacteria, chlorine and other chemicals, as well as heavy metals) or any other water, it is said that even grey water could be cleaned like this. Jon Jandai, an active ecologist and farmer in Thailand is promoting the home filter they made in his eco community, and that they have been using for 10 years for cleaning their drinking water. You can find tutorials and videos about it on the web.

Either you decide to collect rainwater only for your garden, or for drinking it yourself, or if you add a home made or bought water filter, you can search for a local institute to get your water tested (acidity, bacteria, heavy metals,…) to make sure about the safety of the water you are drinking.

A “trash valley” on Koh Mak island, Thailand. Not depending on water bottles supply is better because plastic and other waste are not easily handled on small islands.

Perfect for remote areas and islands

It is very useful to collect rainwater on an island, because there might be no water treatment facilities and it is also a good way to decrease the use of plastic bottles, which produces damaging waste on islands that cannot manage over production of waste. It is also easier than carrying bottled water from the main land, by boat, then by hands and scooter to your house. The rain water is (almost) free and it’s home delivered by the clouds.








Advantages of collecting rainwater

In the future, the number of people drinking rainwater on the Planet may increase, or should, with the world population growth, rapid urbanization, pollution of lands and rivers, the industrialisation of agriculture and inefficient agriculture techniques (open lands and uncovered soils loose 80% of the water) which induce a massive use of water. In that actual situation, access to fresh drinking water could become our first challenge during this century, it is already a challenge for about 20% of the people on the Planet.

When harvesting your own drinking water, not only can you contribute to your own water supply, increasing your own autonomy and security, getting water free of chemicals used by city water treatment, you also help decreasing the use (production, transport and waste management) of plastic bottles, you decrease in the same time the amount of chemicals from the plastic bottles that can migrate into your body cells or blood, you ecologically participate to saving water, you feel more free to use your own water without feeling bad for the planet, and you save money. If you used to buy plastic bottles, you even save time and energy because the water falls directly into your water tank without needing to go to get it. Water collecting can also reduce soil erosion, as the water falling on the roof is intercepted before falling onto the ground.

Harvesting water for watering your garden, cleaning, toilet, or other uses is easier because you don’t need it to be as clean as for drinking it. It is nonetheless a very important step you can make to ecologically save water and money.


Buying and installing a water collection system or home filtering system, making it clean and safe (checking the roof material if it brings dangerous matters in the water), maintaining it, has a money and time cost. If the disposal is not properly closed, it can lead to mosquitoes breeding, and if it is not clean you can feel ill (you should make your water analysed if you have any doubts). It also takes some space on your land. However, once this investment done, it is done for many years.

A few things to remember:

Microbiological and chemicals are the main risks in drinking/cooking water.

– Rainwater is generally safe to drink (as published in the study of the Monash University from Australia (ScienceDaily, 6 November 20092009) that compared the health of families drinking rainwater and those drinking filter treated rain water).

– Regular chemical or microbiological testing, this will for example check if there is no E. coli.
– Rainwater collection doesn’t need to be tested or perfectly clean for home use such as watering the garden, washing cars, toilet, shower,…

– People who are immuno-compromised (babies, elderly people, severe illnesses,…) should disinfect the water first (boiling, UV light).

– Boiling water can kill most of (but not all) the germs and bacteria, but it doesn’t take away heavy metals, chemicals, and other pollutions.

– For human consumption (drinking and cooking) it is better not to drink rainwater in zones that have heavy traffic, industries or incinerators.

– Check the material of your roof, it must be free of lead-based paintings, bitumen- based material, freshly applied acrylic paints, some new types of tiles may be also dangerous,…

– To prevent contamination risks, the rainwater tank and catchment area need some low maintenance, but it’s important to make this maintenance. For example, cleaning leaves and birds drops away from the roof, checking the accumulation of sludge in the tank and removing it.
Don’t collect the water from the first rain after a dry period, this water is cleaning your roof.

– Fluoride is considered by dentists and other doctors to be a supplement that we should take on a regular basis, this is why it is commonly added to treated drinking water. Rainwater does not contain fluoride, so you may have to find another source of this element if your major water consuption is rainwater. If you don’t want fluoride in your water, then rainwater is a good option.

Further considerations

Rainwater collection in jars or thanks is based on long lasting materials, for example a Thai Jar should last 20 years, which is far better than use and throw plastic bottles (that are used for about 10 minutes to a few hours, but will be a waste for 150 to 1000 years). This kind of system is sustainable. However, the best water system would be a living system, that would be self maintained, such as a roof with filtering plants, or other systems that could last “forever”. Permaculture and other fields of study and experimentation propose different water collection and filtering systems that would be self sufficient and “ever lasting”.

How big should be your water tank? This page can help you to calculate the size of tanks needed for your consuption.

Sources and more information about rainwater quality harvesting:

The Australian government’s notice on the web.

The United Nations’s page about Thailand’s rainwater harvesting, and Examples of rainwater harvesting and utilisation around the world.


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  • Elvis M. Ives February 26, 2019 at 1:31 pm

    I read out the post There are many new things to learn. You wrote it amazingly. thanks for sharing such an informative post.

    • author March 18, 2019 at 11:58 am

      Thank you ! :)

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