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The Basics Everyone Should Know About Rainwater Harvesting When Building a Home

We talk about 6 things to consider when building a home that incorporates rainwater harvesting.

Building a home is possibly one of the most exciting things someone can do in their lifetime. There is a lot to consider in the home building process, but did you know one of them is where you get your water from? If you haven't considered using a rainwater harvesting system before, you will by the time you are done reading, and if you have, you probably have some questions about the process and materials you should be using to build your new house.

Roofing Material

A roof is essential to a house; it helps to keep out nature, but it also diverts water away from your foundation. With a rainwater retention system, the roof is key in the water collection process; however, not every type of roofing material is compatible with a harvesting system.

The Best Types of Roofing

  • Metals including tin, steel, and aluminum
  • Clay tiles
  • Concrete or cement tiles
  • Ceramic tiles
  • Rubber
  • New fibrous cement (older fibrous cement roofing could have asbestos, so it's best to have a professional check it out.)
  • Most asphalt tiles (some won't work for rainwater harvesting, so you should work with a rainwater harvesting professional to ensure your roof is safe for water collection.)

Roofing Materials to Avoid

There are plenty of roofing materials that work with rainwater harvesting systems, but there are a few that don't.

  • Copper is expensive and can leach into rainwater.
  • Lead flashing is still used in some parts of the U.S., so ensure that there is no lead in your roofing material.
  • Cedar or other wood shingles are often treated with fire retardants and sometimes biocides to prevent the growth of algae and moss. They can leach these contaminants into the water, and wood that isn't treated tends to retain mold and algae, which can also get into your drinking water.

How Much Rain Will My Roof Catch?

There is no way of knowing exactly how much water your roof will catch down to the gallon, but historical rain data and a little math give us a pretty close estimate. Approximately 550 gallons of rainwater can be collected for every 1,000 square feet of collection surface per inch of rain. Precipitation varies by region, but, for example,  the average yearly total rainfall for Tennessee is about 54 inches. Since the average roof is around 3,000 square feet, you can assume it would collect almost 90,000 gallons of water annually.

Water Reliability and Quality

When the water you drink originates from your roof, it is only natural to question its quality considering everything else that lands on your roof, but the quality of water you get from our rainwater system is second to none. Before we get to the fantastic quality of rainwater, we should touch on the reliability.


Since most of the rain we see washes down drains and into the ground, it can be hard to visualize just how much water can be collected in a single rainfall. In many cases, people can use rainwater for 100% of their daily needs, but if it does ever run out, we have options to maintain a steady water flow to your house. In addition, because of the proximity to the house and powerful pumps, you will experience better water pressure than wells and at least equal pressure to city water. Finally, unlike your connection to city water that can be cut off or an unreliable well, your rainwater tanks will always be available and refillable.


Rainwater is sometimes confused with the same quality as well water, but rainwater is one of the purest forms of water possible. First, rainwater is not drawn through the ground like well and city water, so it is always soft. Second, rainwater never comes in contact with other ground contaminants like pesticides. However, rainwater is not necessarily safe to drink if it doesn't go through the right process because it can still come in contact with air pollutants and contaminants from the roof, like bird droppings or decaying organic matter. Our rainwater harvesting system uses a multi-step filtration and purification process that makes the water that reaches your home the highest quality water you can find.

Whole Home Integration

Thanks to today's technology, you can run your home off the grid with a rainwater harvesting system. Since the water that gets to your house is pure and pressurized, it can be used for drinking, cooking, washing, and cleaning.

During the planning process, there is another benefit of rainwater harvesting to consider. In most cases, newly built homes need some stormwater management like a retention pond which can be costly and an eyesore. A rainwater harvesting system can not only manage stormwater, but unlike a retention pond, it adds value to your home.

One concern that homebuilders have with installing a rainwater harvesting system is that they could run out of water. In the unlikely event of that happening, our harvesting system has a couple of failsafes to ensure there is always potable water for your house. If the water level gets too low, our tanks can automatically switch to city or well water until they are full. If you want to be completely off-grid, all our tanks have ports so you can refill them from an outside water source.

Cost Comparison to Well or City Water

Like most renewable resources, a rainwater harvesting system will pay for itself over time. According to the Department of Energy, the average cost of water in the U.S. is $3.38 per 1,000 gallons. However, that cost can vary anywhere from $1 to $8 per 1,000 gallons depending on where you live. Well water isn't associated with a monthly bill like city water, but it also comes with its own hidden costs like water purification and softening. With rainwater, you get many hidden benefits that save you money over time.

First, you don't have the upfront costs of investing in other systems in the home like reverse osmosis and water softening. In addition, you don't have any of the regular maintenance and upkeep that those systems require. Secondly, everything in your home, from the pipes to the appliances, will work better and last longer because they are not being ravaged by hard water.


How does rainwater make it from the roof to the house?

As soon as the rain hits the roof, it rolls down to the gutters, transporting the water through a screen to filter out large particles. The water is then held in an antimicrobial tank until it is needed. When you turn on a water source, the water is pumped through a filter to remove contaminants and a UV light to kill bacteria. As a result, the water reaching your house is clean and safe.

Where do rainwater harvesting tanks go on my property?

Your harvesting tanks can be fully buried, partially buried, or above ground. The location of the tanks will depend on your lot size and building plan.

What happens in a drought?

Before installing your harvesting system, we pull the rainfall history of your area for the last 100 years so you know how much water you can expect. If there is a situation where your tanks are low, they can automatically switch to well or city water, or you can call the fire department to refill them for a small fee.

Don't Miss An Opportunity

If you are in the process of designing or building a home, now is the perfect opportunity to install a rainwater harvesting system. Installing during the building process saves money on multiple fronts, including saving time and space on water treatment systems and not having to dig up an already landscaped lawn. If you have more questions about the benefits of rainwater harvesting or are ready to set up a consultation, contact us today.

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