5 Advantages and Disadvantages of Rainwater Harvesting

Posted by
Cameron Wise on February 24, 2023

Rainwater harvesting may seem like an inefficient way to provide extra water for your home, but many Americans utilize storage tanks to supply hundreds of gallons of water for outdoor uses. Not only is collecting rainwater great for homes that practice it, but it is also beneficial to the environment. Below you can find information about what rainwater harvesting is and the advantages and disadvantages of practicing it.

What is rainwater harvesting?

Rainwater harvesting is the process of collecting rainwater as it runs off a roof. Rainwater storage tanks can be located above ground or underground, and they are popular in areas where gardening is common and where drought is a threat. Stored rainwater is used for non-potable applications and can become potable if a water filtration system is connected between a storage tank and a home. Common non-potable uses for rainwater include washing cars, gardening, and watering a lawn.

Rainwater harvesting laws vary greatly by state, but most states have no restrictions on how much rainwater can be collected and what it can be used for. In fact, many states give incentives, such as tax breaks, to those who collect rainwater because of the positive effects rainwater harvesting has on the environment. The Federal Energy Management Program has published this map to illustrate the water harvesting restrictions for each state.

Learn more: Above Ground vs Underground Water Storage Tanks


What are the advantages of rainwater harvesting?

1. Good for the environment

Rainwater harvesting is good for the environment because it prevents rainwater from having a negative effect on soil. When rainwater collects on the ground, it causes soil particles to separate, decomposes soil aggregates, and moves eroded sediment. All three of these effects contribute to soil erosion, an environmental factor that compromises the quality of ecosystems and the ability to grow crops.

Another negative impact rainwater has on the environment is runoff. Runoff is rainwater that flows on surfaces, such as roads, parking lots, and rooftops, that does not absorb into the ground. This water carries pollutants present on these surfaces into groundwater, streams, and lakes. Collecting rainwater before it reaches the ground prevents some chemicals, sediment, and debris from entering water sources.

Rainwater harvesting also helps save energy. Because collected rainwater can be used for outdoor applications that do not require filtration, energy is not used on filtering water that does not need it. Rainwater harvesting prevents water treatment plants from using excess electricity, pumping stations from using extra power, and sewer and water line repair machines from burning more fossil fuels than necessary.

2. Saves money

Rain barrels and other above-ground water storage tanks have very low maintenance costs, so the initial expense of a system is a high percentage of its total cost over the course of its life. If you have a regular need for water for your outdoor applications, rainwater harvesting can save you a substantial amount on your water bill. According to a survey by the DC Urban Gardeners, a network of gardening enthusiasts in the nation’s capital, rain barrel users saved an average of $35 per month in the summertime. With a 165-gallon Norwesco storage tank costing just below $400, you can make up the cost of the system in 4 to 5 years. Rain barrels can last for over a decade, so they more than pay for themselves if they are properly maintained.

If you have a whole-house water filtration system, rainwater harvesting will save you money on your filtration system’s maintenance. Since water used for outdoor applications does not need the filtration that potable water does, your point-of-entry filtration system will not filter water that does not need to be. Filtration systems need maintenance once a certain volume of water has passed through them, so causing fewer gallons of water per month to pass through them will prolong the life of your system.

Learn More: What Is a Rain Barrel and How Does It Work?

rain in gutters

3. Provides water in times of drought

Residents of states that are prone to drought, such as California, Montana, North Dakota, and South Dakota, greatly benefit from a rainwater harvesting system. In urban areas, sidewalks and roads cause less rainwater to enter groundwater than in rural areas, so harvesting rainwater in urban areas prevents water from being wasted. It also prevents water that does enter groundwater from collecting chemicals and debris when flowing on sidewalks and roads.

While some states, such as Illinois, Colorado, and Nevada, have restrictions on what harvested rainwater can be used for, most states allow rainwater to be used for potable purposes. With appropriate water filtration systems in place, rainwater can be purified to a safe form for drinking. In areas where water restrictions are put in place during times of drought, collecting rainwater can help save some headache by supplying extra water to a home. Even small amounts of rainfall can fill a large storage tank if the storage system efficiently collects rain from a roof. A 2,000 square foot roof can collect just over 1100 gallons of water from just one inch of rain. According to the Philadelphia Water Department, the average American household uses around 300 gallons per day. This means that one inch of rain can supply a household with water for almost four full days.

4. Easy to install

Rain barrels and other above-ground water storage tanks are quick and easy to install. A simple rain barrel can be installed yourself following the steps listed below.

  1. Locate the area where the rain barrel will be installed. If you know which downspout most rainwater runs through, place the barrel under this downspout.
  2. Add connections to the rain barrel. Any hose connections or spigots should be added at this time. If you purchase a collapsible rain barrel, this step will be more involved.
  3. Prepare the ground around where the barrel will go. If you are not placing the barrel on concrete, you will want to dig and add gravel beneath where the barrel will be placed. Placing a rain barrel on an unstable surface can cause stress on the barrel when it stores water.
  4. Connect the barrel to the downspout. In this step, you need to measure and cut the downspout to accommodate the barrel. Once the downspout is cut, you will add a downspout diverter to the cut section that allows water to be redirected to the tank.
  5. Place the barrel in its destination. Ensure the barrel is level so that the weight of the water is equally distributed across the tank.
  6. Divert the overflow of the barrel away from the foundation of your home. Water can cause hydrostatic pressure on a foundation, causing cracks and leaks to form.

If you purchase an underground storage tank, you will need to consult a professional to install your tank for you. While the installation process may seem like a headache, underground tanks can last up to 40 years and sometimes even longer if installed and maintained properly.

Learn more: Above Ground vs Underground Water Storage Tanks


5. Ideal for outdoor applications

Not only is rainwater suitable for outdoor applications, but it is also better for some uses than city-treated water is. Washing your car with rainwater, for example, can be easier on your car’s paint than tap water. Rainwater does not contain the salts, chemicals, and minerals that treated water possesses, so it is more beneficial to wash your car with rainwater than tap water in most cases. If you live in an area with high levels of air pollution or smog, rainwater may be worse for use in outdoor applications than treated water. As rain falls, it collects contaminants in the air before reaching your storage tank. If you are unsure if your rainwater is contaminated, you can check the water quality with a home water test kit.

Another great application for rainwater is gardening and agriculture. Rainwater contains nitrate, a nutrient that plants need to thrive. While large debris will be filtered out before entering a water storage tank, rainwater collects contaminants from leaves, bird droppings, and insects, as it flows off your roof. These contaminants are beneficial to plants, so watering your garden with rainwater can improve their health. You should exercise caution while using rainwater around edible plants. If rainwater contacts the edible parts of a plant, it can contaminate whoever eats from the plant with the same contaminants that benefit its growth. Irrigation systems circumvent this issue by watering plants effectively while avoiding contamination of their exposed parts. Rainwater harvesting is also beneficial for agriculture, particularly in areas where water scarcity is an issue. Rainwater can help keep crops hydrated during dry seasons by irrigating crops and complementing rainfall.

watering plant

What are the disadvantages of rainwater harvesting?

Just like with anything, the benefits of rainwater harvesting must be weighed against its disadvantages. While collecting rainwater is beneficial for many people, it may not be suitable for others.

1. Can be expensive to maintain

A properly installed water storage tank requires cleaning anywhere from once every 6 months to once every 5 years. However, if a tank is not properly installed, it can be very expensive to repair or replace. For above-ground tanks, if the ground is not stable or level, stress can cause cracks to form on the exterior of the tank. While cracks are fixable, they do compromise the structure of the tank and may lead to additional damage. Underground tanks that are in an improper location may become damaged by excessive weight, such as a parked car, on the surface. For tanks that require a professional to install, hiring the right people for your tank can mean the difference between an efficient system and a costly one.

In the winter, above-ground storage tanks must be either insulated or stored indoors if the temperature drops below freezing. When exposed to sub-freezing temperatures, water in the tank expands and can damage the tank’s structure, causing cracks to form. If you wish to use your tank in the winter, insulating it comes at an additional cost.

2. Can possess contamination risks

Some rooftops contain lead and other elements that may be harmful in some applications. While rainwater is highly beneficial to plants most of the time, water that contains lead is toxic to plants and should not be used for gardening. If you are concerned about lead in your rainwater, you can test your water with a PurTest Lead Test Kit. If you are using your water for potable applications, such as drinking and cooking, you will want to install a water filtration system that will take care of these contaminants. A reverse osmosis system, for example, removes most types of contaminants and makes water potable.

3. High initial cost

While rainwater harvesting systems can help you save money in the long run, they do have a high initial cost. Depending on the size and type of tank you choose, a rainwater harvesting system can cost anywhere from a few hundred to a few thousand dollars to purchase and install. If you move or are unable to use your system for another reason, you will not reap the benefits of your initial investment. However, if you have consistent demand for rainwater and know that you will not relocate anytime soon, a rainwater harvesting system is a worthwhile purchase.

4. Storage limits

While rainwater harvesting systems are efficient at collecting rainwater, the collection is only as efficient as the size of the tank. While large-capacity tanks exist, they come with an added cost in both the tank itself and in installation, so weighing the need for a larger tank and the price discrepancies between sizes can be tricky.

5. Unpredictable collection amounts

If you have a consistent need for rainwater, the weather may not cooperate with your demand. If your area is prone to drought, you will need to be more conservative with your water usage than those that are not. If you purchase a large tank and the rainfall you receive is not sufficient to fill it, then the cost of the tank will take longer to make up for itself.



If you have any questions about rainwater harvesting or water storage tanks, please do not hesitate to contact us.

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