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6 GOLDEN RULES TO COLLECT ROOFTOP RAINWATER: MAKE YOUR ROOF WORK HARDER FOR YOU

Updated: Nov 23, 2025

Rooftop rainwater harvesting systems are trending this season. How you can help solve water shortage crises, one rooftop at a time


Key Points:

  • Easy, affordable and effective: simple rooftop rainwater systems allow you to harvest and use water for your own needs

  • Collecting rainwater begins with selecting the right roof for your home

  • See how a new home in Arizona’s severe drought zone maximizes water supply with an innovative rooftop rainwater collection system

metal roofing rainwater harvesting system
An innovative metal roof rainwater harvesting system is the star of the latest Build Show project https://www.youtube.com/watch?v=HnAtex2Scwc

Precious water. For lots of homeowners living in arid and drought-prone climates, every drop counts.


With the fall and winter rainy and snowy season now beginning, there’s a simple and straight-forward way to take advantage of rainwater, ice and snow melt to store and use for your own purposes. Rooftop rainwater is an accessible and economically viable option, and the good news is it’s easy to do.  


Basically, instead of allowing water to drain away, put your gutters to work and channel all that water into a storage vessel instead. Storage can be as small as rain barrels that keep a few gallons of non-potable water handy for watering plants and augmenting irrigation systems, or they can be as elaborate as large cisterns that supply an entire household’s potable needs (when properly filtered, disinfected and tested).


Rooftop rain collection systems can make a big difference to your water supply: One inch of rainfall on 1,000 square feet roof yields an incredible 623 gallons of water.


Well-known architect and social media influencer Steve Baczek of the Build Show recently showed off a home building project in Cave Creek, Arizona, located in an area that gets only 11 inches of rainfall a year. Using the right roofing materials and an innovative design to capture and maximize every drop, Baczek shares why metal roofs and rainwater systems make perfect sense in his just-released video https://www.youtube.com/watch?v=HnAtex2Scwc.


Rainwater harvesting 101: It’s all about the right rooftop

As Baczek points out, when it comes to home rainwater harvesting systems, your home’s roof is one of the single most important components. Some experts warn that older shingled (asphalt) roofs made before 1980 may contain asbestos which is hazardous if disturbed. Even if your shingles are new, not all varieties are safe for water collection because they can leach contaminants and large chunks of grit. Some experts say to avoid collecting water from an asphalt shingled roof in the first three years following installation, to give the installation adhesives time to off-gas.


While research varies on whether toxins may leach from materials like asphalt, the real concern when it comes to rainwater harvesting is how best to reduce the potential contaminants that grow on the roofing material itself. Compared to other materials, metal roofs have much lower concentrations of dissolved organic carbon and other bacteria. That’s because metal roofs are often coated in anti-microbial paint systems, meaning they will shed larger organic matter more quickly and don’t have cracks and crevices that may allow harmful microorganisms to grow. Galvanized and Galvalume metal roofs also are ideal as they are coated with a layer of zinc which seals the material, preventing rust and lowering levels of iron in the water.


Metal roofs also are durable and strong enough to withstand the intensity of heavy rain and weight of snow and ice, and well-built metal roofing systems with properly designed gutters and downspouts provide an easy and efficient path for water to travel, even for low-sloped roofs.


No matter what type of roof you may have, experts emphasize that any water collected should always be filtered, and decontaminated before use. This is critical for any harvested water used inside the home for consumption.


And speaking of metal roofs and rain, it’s a common myth that metal roofs are noisier than other types in heavy downpours. The truth is that when properly insulated and installed, metal roofs are no louder than any other type of roofing materials, so you can go ahead and harvest rainwater from a metal roof without worry.


Key rooftop components: What to consider

While rainwater collection systems are typically very basic and easy to use, the best time to plan for them is when installing a new roof or reroofing your home. Working with your installer, a few key things to know:


  1. You can collect rainwater from any type or shape of gutter. No special gutter is needed.

  2. Your gutters should have protective screening to help keep large debris out.

  3. Your roof grade matters: steeper slope allows for quicker run off and less chance for potential organic containments to build up

  4. An additional filtration opportunity is available with the installation of a rain head (downspout filter) that allows for more self-cleaning. A first-flush diverter also helps prevent the first flush of contaminated rainwater from entering your storage container/tank.

  5. Ideally, you should already have a plan for storage in place so your installer can plan for and retrofit downspouts and connection points as appropriate.

  6. Keeping your roof clean and ongoing maintenance also is important. Fortunately, today’s quality metal roofs are exceptionally easy to clean with gentle, non-toxic methods that call for plain water and some mild, biodegradable soap if needed. 


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