Install a Rainwater Catchment System

Rainwater catchment systems harvest rainwater for the homeowner’s non-potable needs. Modern versions of this ancient technology offer plumbers an opportunity to capitalize on a growing trend in green building techniques.

“[Catchment systems] save water and energy,” says Doug Pushard, founder of HarvestH20.com, a website that offers information on sustainable water management practices. “It’s the direction the country and general population is headed. They save drinking water, which is becoming more and more precious.”

As beneficial as catchment systems may be, they’re complex and take a good deal of knowledge to set up. It generally requires retrofitting, and the difficulty of installing a system depends largely on the layout of the building and its surroundings. However, she says that if you come across a very complex layout, you’ll be much more prepared if you know the supply and demand is matched up. To figure out how much rainwater you can collect off your roof, Pushard offers a formula on his website for the amount of water that can be captured: roof square footage x .623 gallons per square inch of rainfall x annual rainfall.

Here are some things you need to know before installing one:

Tank size
First, determine what the demand for non-potable water is for the home or building. Look at water bills to see how much water your client uses per month, says Pushard. Or you can recommend a simple test with a 5-gallon bucket to see how many gallons are used in a week. The bucket test is done by putting a bucket under the building’s water spout to determine approximately how much water comes out in a minute. Pushard then says to multiply this amount by the number of minutes outdoor faucets are run each week.

Pushard’s website also offers an online calculator that can help plumbers and their clients determine a home’s water footprint. Tools like this can help determine how much water is being used.

Tank location
Pushard says that an above ground tank is less expensive than an underground one, but it will only be able to capture during the non-freezing months of the year. However, an underground tank can capture water and snow year-round, so it may be worth it for homeowners in northern regions of the country. Also, an underground tank requires less maintenance and takes up less space.

Capturing the water
“Rain barrels and above ground tanks are good to install near the house and typically underneath the downspouts,” says Pushard.

For an underground cistern, Pushard says it should normally be placed where gravity can fill the tank and eliminate the need for the pump. If possible, it should be placed where it can “maximize catchment and minimize the runs of PVC pipe to reach the cistern.”

If buying a pump turns out to be necessary, Sarah Lawson, a water specialist with Rainwater Management Solutions, a rainwater and stormwater management solutions firm headquartered in Salem, Va., recommends buying one from an established company so buying necessary replacement parts won’t be difficult to do down the line.

Water filtration
“One of the most important steps a designer or installer can take in developing a rainwater catchment system is ensuring that the water is filtered before it enters the tank,” says Lawson. “This prevents leaves and other debris from building up in the tank which degrades the water quality.”

For rainwater filtering, Pushard recommends installing gutter guards or a screen to keep leaves, animals and debris out of the water. However, Benjamin Sojka, vice president of design for Rainwater Management Solutions, says if the homeowner doesn’t want the arduous task of changing the screen regularly, he recommends installing a vortex filter, in which water comes in spinning from the side through two vertical screens that catch debris. Vortex filters are self-cleaning and are up to 95 percent more efficient, Sojka says.

Avoiding cross-connection with drinking water
“One of the most frequent sticking points in designing and installing a rainwater harvesting system for a residential or commercial building is providing a back-up water supply while avoiding cross-connection, an opportunity for non-potable rainwater to enter the potable water supply,” says Lawson.

She mentions that cross-connection can be avoided by simply setting up two spigots for watering, keeping the non-potable water completely separate from the potable water system. However, to avoid the hassle of manually switching a hose over, Sojka recommends using one of two methods:

A reduced pressure zone assembly (RPZ) is a type of backflow prevention device that uses springs and mechanics to keep water flowing forward but not backward, which would cause contamination.

An air gap is an actual physical break or separation in the pipes that allows water to drop into a funnel so that is unable to flow back in. An air gap doesn’t use any form of mechanics.

Acquire the skill of rainwater catchment installation and your company will stand apart from the competition. You will also have the opportunity to tap into a market that’s experiencing “pretty extensive growth,” according to Lawson. Pushard agrees and recommends visiting the American Rainwater Catchment Systems Association’s website, to find out more about classes and certification for rainwater catchment professionals.