The cistern, blended with the landscaping.
Project data
Authors Ole Ersson Portland, Oregon 1996 Rainwater harvesters Download Upload your project too!body.poncho-dark-mode .mw-parser-output .mw-ui-button{background:#303134;border-color:#3c4043;color:#bdc1c6}@media screen and (max-width:500px){.mw-parser-output .button .mw-ui-button{display:block;margin:.5em 0}}

In January 1996 we installed a rainwater catchment system to capture Oregon's abundant rainfall. Portland receives between 3 and 4 feet of rainfall annually. During a gentle rain a typical Oregon downspout sheds several gallons per minute. Our twelve hundred square foot roof captures on average 3600 cubic feet (27,000 gallons) of water per year. In 1998 we received approval from the city of Portland to use this water for all household use.

Materials

This system, which cost less than $1,500, consists of the following components: • A 1500 gallon plastic cistern, approximate cost:$500. Our tank was made by Snyder Industries. Contact local agriculture or farm stores for the best prices. Or check yellow page listings for tanks. Here is a link to an Oregon dealer.
• A 1/2 horsepower shallow-well pump to pressurize the water to between 20 and 30 psi (pressure is adjustable), approximate cost: $250. I utilized a Jacuzzi brand pump. • Plastic (outdoor PVC and indoor CPVC) piping to connect to the household cold water system. • Two particulate filters in series, rated at 20 and 5-micron particle size, approximate cost:$20 each; replaceable filter cartridges cost $3-5 each. • An ultraviolet light sterilizer capable of sterilizing water at 10 gallons per minute. This appliance was recently approved for use in Oregon. I used the PURA (1-800-292-PURA, Valencia, California) model UV20-1, cost approximately$350. Uses about 40 watts. Fluorescent ultraviolet light rated at 9600 hours, about one year of continuous use. Replacement cost of fluorescent tube: about $80. • Screen covering the cistern to prevent entry of mosquitoes and to catch any large particles that make it past the gutter screening. • A roof-washer which wastes the first 7.5 gallons of captured water which has "washed" the roof. Once the roof washer has filled, the rest of the water flows to the cistern. See below for details. • A 20 gallon water butyl rubber diaphragm pressure storage tank, approximate cost:$150.
• A reduced pressure backflow prevention device. This was required by the city to prevent flow of rainwater into the public system. Cost: $120. This would not be necessary if we used rainwater exclusively. However, Oregon has very dry summers and our cistern is exhausted by July. We currently depend on city water during the summer. The city requires annual inspection of these devices, costing about$30. (See photo below.)

Advantages

One notable advantage of rainwater is its softness. Rainfall in the Portland area contains about 5 mg/liter of dissolved minerals. Compare this with some hard groundwater which exceeds 500 mg/liter. Portland city water, which has an exceptionally pure source, is rated at 12 mg/liter.

Additional information

According to two officials in Alaska and Hawaii with whom I have communicated, there is a long established tradition of rainwater collection in some parts of their states. According to Sourcebook Harvested Rainwater, in some areas of the Caribbean, new houses are required to have rainwater capture systems. Hawaii apparently is currently developing (or has already developed) guidelines. In Oregon, there is no regulation of water quality for individual residences -- this is left up to the homeowner. The only regulations I have come across relating to rainwater harvesting are from Ohio, whose Department of Health Administrative Code regulates private water systems. Note, in particular, Rules 3701-28-09 Continuous disinfection and 3701-28-13 Construction and surface design of cisterns, hauled water storage tanks, and roof washers.

A great resource for rainwater harvesting information is Warwick (Coventry, United Kingdom) University's Development Technology Unit Roofwater Harvesting Programme.

Update Summer 2002

A different style of roof washer. This summer we installed a commercially available roof washer that uses a programmable valve to divert a rain's first flow away from the cistern. A purported advantage is the absence of standing water that can stagnate and potentially contaminate the cistern water. (This could happen, for example, if the trickle valve on the conventional device were to clog or it were left closed.) Below are two photos of the system with this new device. The first photo shows the roof washer mounted on a window frame near the cistern. Rainwater, which enters from the two downspouts above, can be observed from inside the dwelling. The first flush is diverted downwards into a holding barrel. An overflow hose from the top of the cistern also empties into this barrel. Post-flush water enters the cistern via the roof washer's side port through a screened cistern entry hole. The barrel overflow is directed to a swale in the middle of our back yard.

Update January 2004

An American-made roof washer and rainwater sculpture. I never was able to get the SafeRain roof washer to function properly in Oregon's often drizzly weather. Either the roof washer diversion valve would not properly close, thus diverting all the rainwater into the overflow, or it would not open after the rainfall event ended, retaining dirty water in the device. I attempted numerous times to adjust it, all to no avail. Unfortunately, for this reason, I can not recommend this device. The last straw came during recent freezing weather when the device froze with water in it, rendering it non-functional. Therefore, recently, I installed a newer style of first-flush device. This device is considerably less expensive (approximately $66 versus$140 at currency exchange rates 22 Jan 2004, including shipping) for North Americans, since it is locally made and uses standard pipe fittings. The first-flush valve kit consists of a hollow ball (see middle two photos below) which, when filled by the initial flow of water, seats itself onto a rubber gasket. This closes the overflow pipe and subsequent rainwater is then diverted to the cistern. After the rain stops the ball empties and the diversion valve returns to the open position. I will post a review of how well this device performs at the end of this rainy season. At this time it already seems to be functioning properly.

At the same time I installed this roof washer I also installed a more elaborate piping configuration (see photo, above, left) leading from the downspouts to the cistern that is intended to act as a water sculpture. Viewable from our dining room window, it will display ten areas of flowing water, depending on the time in a rainwater event and the rainwater flow. During a typical Oregon drizzle, only the left most vertical pipe (see photo, above right) carries water. During a downpour all three pipes will be filled to capacity and additional flow will emerge from the 2" elbow.

Update January 2005

Final roof washer review. Unfortunately, this second roof washer employs the same mechanism as the earlier, Australian, model to reset itself after a storm event. Both devices use a small, hollow, plastic ball that fills with water when rain begins. While the ball fills, the initial dirty rainwater is wasted. When the ball is full, it lowers over a drain hole, causing the remaining clean rainwater to be diverted into the cistern. The problem with both these devices is that their ball depends on a tiny pin-hole to empty their water when the rain stops. However, it is all too easy for this hole to become obstructed with small particles of sand or other debris common in a gutter. The ball then does not drain properly and the device does not reset itself. Thus, both devices required close monitoring and frequent manual cleaning in our system. I regret to say that I cannot recommend either one. My recommendation at this time is to employ a homemade Texas style standpipe roof washer. Its simplicity allows it to be constructed and maintained inexpensively.

We have now sold this house and moved to a different residence. We will work with the new owners who will continue using this system.]]

Page data
Type Project SDG06 Clean water and sanitation Curt Beckmann 2006 CC-BY-SA-4.0 Erssons https://web.archive.org/web/20200107163759/http://kailashecovillage.org/experiments/ [see first revision] 241 Curt Beckmann (2006). "Ersson rainwater harvest and purification". Appropedia. Retrieved August 13, 2022.
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