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In search of the holy grail of rain catchment

By September 26, 2012November 20th, 2019No Comments

It was in the Negev Desert on an archaeological excavation when I first thought about building a cistern in my backyard.

I was a Pomona College Sophomore on a summer internship when I climbed to the top of Masada, the ruins of King Herod‘s desert palace. Perched on the edge of a steep 1,800-foot plateau, Masada stands like a sandy lighthouse watching over the nearby brackish Dead Sea. Built as a luxurious safe house for the Levantine king, Masada is an impressive example of the sustainability of Roman architecture.

Despite getting less than 10 inches of rain a year, Masada has no natural spring or well. Yet Herod demanded it house the aquatic amenities expected of a Roman villa: fountains, steam baths, and irrigated farm land. The secret to this desert oasis was a colossal system of cisterns, which captured more than 40,000 cubic meters of rainwater (about ten million gallons) during the brief winter wet season.

The image of those cisterns stuck with me for years. Recently, I got to thinking about how I could apply Herod’s first century technology to a sustainable 21st century household. Could I supplement the water needs for a family of five by relying on the rain?

I turned to Claremont’s water guru and fellow Sustainable Claremont board member, Richard Haskell to help answer the question. He mentioned that the average Claremont household requires 15,000 gallons of water per MONTH! That was shocking. But after consulting my own water bills, I was embarrassed to learn that my family actually used almost 17,000 gallons per month, or a staggering 200,000 gallons a year!

Now that I knew the demand, I needed to know how much water Mother Nature could supply. According Bernard Field Station records, Claremont averages 16.58 inches of rain annually. Assuming rainfall remains constant, and if I used my 2,800 square foot roof as the catchment system, I could store about 29,000 gallons of rainwater each year. That was nowhere close to the 200,000 gallons I consumed. I’d need a whopping 20,000 square feet of rain catchment to meet those needs, more area than my entire lot (plus the neighbor’s for that matter). I simply didn’t have the land to sustain my water habit through rainfall. I felt like my dream of a mini Masada in my backyard was slipping away.

So where was all this water going? Was the culprit the laundry, a leaky drip irrigation system, or maybe topping off the pool? My monthly bill lacked any specifics. Southern California Edison ‘s home energy efficiency survey—available online—gave more details, although not without controversy. According to SCE, I spent about 25% of my water on landscaping. But some experts felt the SCE data could be misleading. In fact, most studies show that landscape irrigation accounts for as much as 50% of residential water use in Southern California, and maybe as much as 70% or more. Suddenly, I had a new cause. If my cistern could help my lawn and plants stay green while absolving me of a little eco-guilt, I was game.

With new resolve and 29,000 gallons or rainwater to store, I needed a place to put it. Herod’s cisterns were plaster-lined, underground and cleaned out annually to prevent disease and fouling. If I were to build a cistern that would keep away bacteria and algae, and—most importantly—meet modern building codes, I was going to need another expert. This time I contacted Erik Petersen and Lee Krusa at Claremont Environmental Design Group (CEDG).

The environmentally aware architecture firm has designed several cisterns for eco-groovy clients ranging from simple, plastic-lined holes in the ground to giant, self-contained plastic tanks. Innovative plumbing filters out all that muck that comes down the gutters during the first rains, and an electric pump pulls the water from the storage tanks. By my own estimates, my system, using 15 underground storage tanks, would cost about $35,000 in materials and labor. Yikes!

The sticker shock forced another question. Would this water battery ultimately make financial sense? At my current consumption rate, the cistern would only be offsetting my water bill by about $250 dollars annually. As many Claremonters know, water prices are slated to go up considerably, so I guesstimated future water costs might double over the next several decades. Even with that assumption, I’d need more than 60 years to get back my original investment. Building a larger cistern might be more cost-effective and speed up the savings, but that assumed I had the real estate to build it. Regardless, the economic argument for my cistern was marginal at best.

Certainly, there are other reasons for a cistern. Capturing rainwater before it goes down the storm drain limits the pollutants introduced to the ocean. Catchment also reduces local dependency on imported water, and rainwater is tastier and softer than tap water, as well as un-chlorinated. Most compelling to me, cisterns improve your self-sufficiency, especially during natural disasters like those pesky earthquakes we have.

So building a cistern on my property will have to be more about these other factors than just economic motivations. More importantly, my quest for the holy grail of water catchment reiterated the importance of that other c-word, conservation. I’m now watering the lawn less frequently, and I’ve installed low-flow showerheads. We might even consider a hot water recirculating pump to reduce water waste while waiting for the shower to warm up. These small improvements can make a big difference in consumption, which means that the water caught from the skies can have greater impact.

Regardless, I still want a catchment system. Call it nostalgia or paranoia, but I plan to build a modest system next year when we do some remodeling. A man’s home is his palace, and mine deserves a cistern.

Demystifying Sustainability is an initiative of Sustainable Claremont (

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