Myths And Misconceptions About Rainwater Harvesting

As climate change makes drought more prevalent, people are looking for solutions to make their homes and communities more resilient to drought. Rainwater harvesting is a tool to help address such water-related challenges. In many places around the world, rainwater harvesting is nothing new. People have been collecting and storing water in tanks for thousands of years. However, rainwater harvesting is not as common in some areas in North America. For this reason, some people may have some false conceptions about what rainwater harvesting entails. This article will discuss some of the myths and misconceptions people have about rainwater harvesting.

Myth #1: Rainwater harvesting is just tanks

Rainwater harvesting is a term that often refers to tanks that capture and store runoff from rooftops. Capture and storage of water in tanks is referred to as “active rainwater harvesting.” There is also “passive rainwater harvesting.” Passive rainwater harvesting is a system that intercepts and stores precipitation in the soil. This is often accomplished through the construction of vegetated structures such as rain gardens or bioswales. Passive rainwater harvesting is just as important, if not more important, than active rainwater harvesting because these vegetated systems support plant life and recharges groundwater, which is an important source of water in many areas throughout the United States. Hydrated ground cover and landscaping also make an area more resilient to fire.

Active and passive rainwater harvesting can work together to make a robust rainwater capture system. This can be accomplished by installing a bioswale that captures overflow from a rainwater tank.

Myth #2: All rainwater tank systems are more or less the same

Before I became more involved in rainwater harvesting design through my work, I thought all rainwater systems were more or less the same except for the tank size. After working on a few rainwater tank projects, I learned that this is very flawed thinking. Rainwater harvesting systems encompass much more than the tank. You must consider the end-use (e.g., washing, irrigation, drinking), water filtration, the roof material, the tank material, the climate, rainfall patterns, the size of the site, and much more. There are rain barrel kits available for purchase online. These work well for very small systems and are a good entry point to rainwater harvesting. However, systems larger than 55 gallons require more design work and thought if you want them to work well.

Myth #3: Rainwater harvesting is just rain barrels for gardening

When many people think of rainwater harvesting, they think of rain barrels that collect water for a small garden. However, rainwater harvesting is a term that describes a broad spectrum of rainwater capture systems that range in size and complexity. Rainwater harvesting is not just for irrigation. Many people around the world use rainwater harvesting for drinking and washing. In California, there are landowners who have tanks that hold 100,000 gallons or more! These tanks can be used for agricultural purposes and even fighting fires.

Myth #4: Rainwater harvesting is illegal in the State of California

Rainwater harvesting became legal when the Rainwater Capture Act of 2012 was enacted. This bill allows residential and corporate entities to capture rainwater and use it for landscape irrigation and other non-potable uses. Prior to the Rainwater Capture Act of 2012, the State Water Resources Control Board (SWRCB) required a permit to appropriate water from any source, including water falling in the form of precipitation. Now, according to CA Water Code § 10574 (2017), “Use of rainwater collected from rooftops does not require a water right permit pursuant to Section 1201.”

Myth #5: Rainwater harvesting is not worth it if you live in a dry or arid climate

Many people and communities in arid climates have successfully implemented rainwater harvesting systems. Tempe, Arizona, which only receives about 9 inches per year of rainfall, has a rainwater harvesting rebate program for residents. They offer workshops free of charge. Some of these workshops are available virtually. Visit the Events Page on the Watershed Management Group website to learn more about these workshops.

Myth #6: Rainwater harvesting is not practical in cold climates

Rainwater harvesting is definitely possible in cold climates. Tanks can be installed above ground or underground in freeze-prone areas. However, it is important to consider the following when designing a rainwater harvesting system in a colder climate:

  • Configure lines for dry conveyance since standing water could freeze (and cause damage to the pipes) in wet conveyance systems.
  • All pipes should have a minimum slope of 1/8 inch per foot to ensure that water completely drains to the tank.
  • If you choose to put your rainwater tank underground, at least half of the tank should be below the local frost line, and all outlet pipes should be at least one foot below the frost line.
  • Consider insulating above-ground tanks. Cylindrical tanks can be insulated with reflective bubble wrap, straw bales, or hay bales.
  • Consider putting floating heaters in tanks.
  • Drain smaller tanks during the winter. If an above-ground tank is going to remain active during the winter months, make sure to keep the thank level less than 3/4 full. This will allow for expansion during ice formation.
  • Consider purchasing darker-colored tanks and placing them next to a south-facing wall. The heating on sunny days may counteract some freezing.
  • Heat tape can provide internal heating to prevent freezing in inlet or outlet pipes.
  • Make sure overflow water drains away from the tank to prevent pooling and freezing around the tank.

Myth #7: Rainwater cannot be used for drinking water

Some people think that you cannot drink water from a tank. In reality, many people around the world rely on rainwater harvesting for their drinking water. In fact, millions of people in urban Australia regularly drink rainwater. However, it is important that a rainwater system be designed properly if you are going to use rainwater harvesting for potable uses (e.g., drinking, showering, and other indoor uses). This means that the tank material and roofing material on the catchment area should be suitable for drinking water. In most cases, it also means installing a “treatment train” that sanitizes and disinfects captured water. Water treatment can be complicated, so it is important that you consult a professional rainwater harvesting designer if you want to install rainwater tanks that will be used for potable uses.

It is important to note that the California Plumbing Code and the State Public Health Department do not recognize rainwater as a potable source.

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