With more than 30 years’ experience in the residential and commercial water treatment space, Mark Nelson is a Class 1 Drinking-Water Operator and a CBWA (Canadian Bottled Water Association) Certified Plant Operator. As founder and president of Nelson Water in Ottawa, Mark focuses on dealing with challenging water treatment system designs for problem water. He also heads the largest water bottling plant in the city of Ottawa with a delivery network throughout the Valley.

Tasting the rain was a simple pleasure many of us enjoyed as children and some of us enjoy it to this day. But, in many parts of the world rainwater is the sole source of water or perhaps a supplement to a more meager source of clean drinking water. This is referred to as rainwater harvesting and it has gained significant traction in homes, industry, and agriculture. Rainwater can be a boost to your home for a wide variety of tasks, but using it safely is not an extensively covered topic.

Understanding Rainwater Harvesting

We’ve covered the basic concept in the introduction, but the process can vary depending on the exact situation. The collection and storage of rain for drinking, bathing, irrigation, and many other tasks is pretty simple. The rain run-off from a sloped roof or other structure is directed to a storage vessel via a gutter and downspout. The complexity of the system can vary a great deal from a huge cooling tower at a factory to a rain barrel in a garden. Rainwater can be consumed only if it’s filtered and cleaned sufficiently. There are three main types of rainwater harvesting systems, they are rain barrels, wet systems, and dry systems. Let’s take a closer look at each to better understand them.

The Rain Barrel

These are the simplest and most economical systems used to harvest rainwater on a very small scale. This is a plastic barrel that you can find at most home improvement stores that is placed under a downspout from a roof to collect the runoff. A typical rain barrel can hold around 50 gallons of water and the better models have a spigot at the base. This will allow you to draw water easily, you can attach a hose and gravity may supply sufficient water pressure to easier watering. It’s also possible to link your rain barrel to an existing irrigation system for cheaper and easier plant watering duties.

Wet Systems

These systems use a pipe that collects rainfall from the gutters, which then rises up a vertical pipe and fills an underground storage tank. The pipes constantly contain water and this is why this method is referred to as a wet system. But, because the pipes don’t dry out between bouts of rainfall this can cause the water to become stagnant. This in turn can lead to anaerobic fermentation, mosquito infestations, and other problems. For these reasons, it’s advisable to screen the pipe entrances and to drain them weekly. A wet rainwater harvesting system does require more maintenance than a simple rain barrel. But, they are easier on the eye because the storage tank is located underground and it can be located some distance from the home.

Dry Systems

A dry system is essentially a larger version of a rain barrel. A larger tank is installed with pipes that connect to nearby gutters and downspouts. The storage tank is filled when it rains and the dry system moniker is used because the pipes fully dry in between the bouts of rainfall. The tank empties fully due to gravity and large volumes of rainwater can be stored.

Rainwater Harvesting and Pumps

If you’re considering using rainwater in your home or further away from the storage tank you will need a demand pump. Even a simple water boosting pump can move the harvested rainwater to where you need it. Another option is gravity, but this will limit the potential a great deal and the water pressure will drop as the tank empties. If you simply need some extra water to fill a watering can, you will not need a water pump.

Safe Consumption of Rainwater

If you were to drink drops of rainwater as they fall from the sky it would be very safe to drink. This is because the water is naturally distilled and purified as it rises into the atmosphere. The problems begin when the rain falls because certain airborne and surface based contaminants can contaminate this water source. Airborne contaminants can include dust, soot, dirt, and other pollutants which are prevalent in urban locations. When rainwater hits a rooftop or other surface it will absorb pollutants located there prior to the harvesting. So, if you have bacteria, pesticides, bird poop, dirt, dust, and other contaminants on the roof it will be washed into the collected rainwater. As you can imagine, consuming this contaminated water can be harmful to your health.

Treating Rainwater

The type of contaminants present in any given body of water will determine which treatment method will work best. Running harvested rainwater through a reverse osmosis filtration system will remove up to 99.99% of contaminants including harmful microorganisms. Ultraviolet or UV purification can kill virtually any parasites, viruses, and harmful bacteria. Granular Activated Carbon or GAC filters can reduce or remove many harmful chemical compounds. Boiling water can kill microorganisms, but it doesn’t remove heavy metals or other contaminants. After filtration and suitable treatment, it is possible to use rainwater for drinking, cooking, food prep, and other tasks.

In Conclusion

Harvesting rainwater can be an advantage if you want some extra free water for your home and/or garden. This water is fine for your grass, plants, and cleaning the car without any extra treatment. But, if you want to move the water further away from the storage vessel you’re going to need some type of pumping system. If you want to use harvested rainwater for drinking, cooking, preparing food, and making beverages, it cannot be used in its raw state. A pre-filter connected to a UV and/or RO filter with a final GAC stage will clean and filter the rainwater to make it pure. Remember that boiling the water for at least one minute will kill most microorganisms but it will not remove other contaminants. It’s also important to understand that rainwater harvesting is not possible in certain areas to ensure that groundwater sources are replenished regularly.

If you want to learn more about safe rainwater harvesting, contact your local water treatment specialist today.