mater-courtyardEcovie and local partner Heat Transfer Equipment Company (HTE) are proud to have designed and commissioned a greywater system at the Mather Veterans Village near Sacramento, California.  Using the Intewa AQUALOOP process with its commercial level NSF 350 certification, the system is designed to collect shower, laundry, and lavatory water from a 50 unit affordable housing complex for homeless and disabled veterans.  Up to 1200 gallons per day of clean, treated water is available for use in grounds irrigation.

Since the system was commissioned in April and the facility was filled to capacity in June, the AQUALOOP system has been treating greywater to clean NSF 350 standards for subsurface drip irrigation.  Here are some of the key features of the design.  Click here for a process schematic:

  • The system is housed in two 1500 gallon underground fiberglass tanks.  One tank acts as the AQUALOOP bioreactor, collecting water mather-graphicdirectly from the building and the other holds clean, treated water.  One advantage of the AQUALOOP design is that it can be put into a wide range of tank configurations, above and below ground, and does not require a separate catchment tank in many cases.
  • Two full AQUALOOP membrane stations are used with a total of 12 membrane cartridges.  This is a good example of how AQUALOOP is scalable to any size capacity from single family homes to large commercial systems capable of treating thousands of gallons per day.
  • System control features full remote monitoring and programming developed by Bill McCabe at HTE.  All aspects of the membrane bioreactor (MBE) including aeration, transfer, and membrane backwash are controlled in a central control panel which has an internet uplink.  Equipment guru-billdiagnostics, tank levels, and totalized flow are continually uploaded with alerts for any unusual conditions.  The control approach will be the standard or all AQUALOOP commercial systems.
  • An alternating duplex pump set up delivers clean water to a subsurface drip irrigation system for the landscaping.  A valve opens automatically to supply city water in cases where no treated water is available.
  • The AQUALOOP system produces water from greywater that is at near potable water quality.  The only system certified commercial for NS 350, AQUALOOP has passed the stringent 6 month test with no maintenance which helps show just how reliable the process is.  Click here for an overview of NSF 350.

Ecovie and its partner firms would be happy to talk to you about your commercial greywater system needs.  as with the Mather project, Ecovie can write the full system specification as basis of design and be your partner from engineering through commissioning and ongoing support.  Please contact us!





Mather Veterans Village becomes a reality

A plan hatched a decade ago in Rancho Cordova to create housing for homeless and disabled veterans has become a reality.

Representatives from the city and the development team discussed how they put together Mather Veterans Village. The first phase of that apartment project on the former Mather Air Force Base will have a formal dedication this week.

In 2006, Sander and other city leaders met with the federal Department of Veterans Affairs to discuss affordable housing possibilities. As the longtime home of both Mather and Aerojet Rocketdyne, Rancho Cordova has a heavy presence of military veterans, Sander said. So housing for that demographic was a priority.

Working with Sacramento County and the Sacramento Housing and Redevelopment Agency, the city issued a request for proposals for a veterans’ housing project. The particular site on Bleckely Street emerged because it was close to a veterans’ hospital.

Mercy Housing Inc., working with Mogavero Architects, submitted a three-phase proposal that became Mather Veterans Village. As the concept evolved, the project partners also had to figure out the financing for what ended up being a $17 million project for the first phase alone.

Stephan Daues, Mercy’s regional director of housing development, said affordable housing tax credits got the project across the finish line. But the initial boost came from Rancho Cordova, which pledged $1.3 million from a secured housing trust fund.

Sander said that money came directly out of the city’s general fund. But the veterans’ presence in Rancho Cordova, along with a history of fiscally conservative budgeting, helped the city make the case for using money for that purpose, he said.

As the project took shape, it became a mix of new and old buildings. While two phases involve ground-up construction of about 50 units each, another will re-use an existing infirmary building on the site.

Renner Johnston, a principal at Mogavero, said the infirmary ended up being an ideal candidate for adaptive re-use. As basically a concrete bunker, the building already had energy efficiencies, even though they weren’t the goal when it was built decades ago, that could eventually make it zero-net energy

“Every bit of the structure is heavy concrete,” Johnston said, describing how crews removed one wall to put in more glass with relative ease. “You couldn’t do that with a wood building. This is a unique opportunity.”

The infirmary re-use will convert part of the building into transitional housing for recently homeless veterans. The rest of the building will host an array of social services and resources, from meeting rooms to a community space to demonstration kitchen to computer lab. The latter features are already complete, with more to come as the full buildout of the infirmary re-use phase and then the ground-up third phase get underway.

The first-phase apartment units are clustered in a three-story building with both stairs and elevators. That helps disabled veterans access any unit.

Other features in the building include solar-powered water heaters, a greywater system to irrigate landscaping and solar panels for electricity. Johnston said those features reduce both utility usage and bills, in essence making them more affordable.

Residents began moving into the first phase in late June, and entirely filled them within a month. That wasn’t surprising, when veterans make up an estimated 12 percent of the 2,600 homeless counted in Sacramento County last year. According to Rick Sprague of Mercy Housing, Mather Veterans Village already has a wait list of 34.

Both the second and third phase of the project, each with another 50 housing units, could get underway by the end of next year. Beyond that, officials involved in this project said they can see a need for more like it.

“I wouldn’t say we’re done,” Sander said.


AQUALOOP NSF 350 Certified for Greywater Recycling

The AQUALOOP greywater recycling system is now certified under NSF 350 for bath and laundry recycling at the commercial (C) level, the very first and only system to pass these rigorous standards.  This is an important development for the entry of AQUALOOP into the US market since a number of code bodies require NSF 350 listing for any greywater system that will reuse treated greywater indoors.  The following four following plumbing and building codes require NSF/ANSI 350 certification for toilet and urinal flushing.
  • 2015 International Residential Code
  • 2015 International Plumbing Code
  • 2015 Uniform Plumbing Code
  • 2105 International Green Construction Code
This certification helps assure that greywater treated with the AQUALOOP system is suitable for indoor use, can be used for spray irrigation, and is not just sub-surface drip like most other types of greywater treatment.  NSF 350 also assures that Aqualoop treated water can be stored for extended periods and is not subject to the typical requirement that untreated greywater be used or dumped within 24 hours.  As state and local codes adopt these mantional and international standards, NSF 350 will become a necessity for any greywater process.
The NSF certification process entails a rigorous 6 month operating test in which no mainetnance is allowed and water is tested 3 times a week for a wide range of parameters including tubidity, BOD (biological oxygen demand) and biological activity (e.coli proxy).  The water tests for commercial listing are more stringent than the residential listing and as such makes the commercial listing much more difficult to achieve.  In addition, the commercial test is 4.5 weeks longer than the residential test.
Of special note is that the Aqualoop MBR (membrane bioreactor) process is simple with a only three basic steps; pre-filtration, biological digestion through aeration in a fluidized bed, and ultrafiltration.  NO additional disinfection was required to meet the NSF 350 water quality standard.  This mean there is no need for a UV unit or chlorine addition.  This help reduce capital cost, mainetenance, and reliability.  Due to the membrane filter cartridge design, the system is scalable from small residential to large scale commercial sized systems.
If interested in learning more about Aqualoop, please see or

Plumbing codes adopt NSF water reuse standard

From:  Supply House Times

1 April 2016

To help address water scarcity and drought issues, four international plumbing and building codes — 2015 International Residential Code, 2015 International Plumbing Code, 2015 Uniform Plumbing Code and 2105 International Green Construction Code — now require that water reuse systems used for toilet and urinal flushing comply with NSF/ANSI 350 to ensure proper treatment of graywater.

NSF International, a global public health organization, developed NSF/ANSI 350: Onsite Residential and Commercial Water Reuse Treatment to standardize the material, design and performance criteria for water reuse systems.

Water reuse systems reduce costs associated with energy and water use by treating water onsite. In areas such as California, where water scarcity is a growing concern, these systems can provide an additional source of critically needed water and reduce the strain on municipal resources.

Under these codes, should a builder choose to use an onsite water reuse system, certification to NSF/ANSI 350 is either required or constitutes a path to acceptance under these codes. NSF/ANSI 350 certification ensures that water for toilet and urinal flushing (and in some codes for surface irrigation) is properly treated for use in these applications.

NSF/ANSI 350 establishes material, design, construction and performance requirements for onsite residential and commercial water reuse treatment systems. It also sets water-quality requirements for the reduction of chemical and microbiological contaminants for nonpotable water use. Treated greywater can be used for restricted indoor water use such as toilet and urinal flushing, and for outdoor unrestricted water use such as lawn irrigation.

The standard requires 26 weeks of continuous testing with regularly scheduled sampling throughout, typically three days a week. This lengthy testing time with high sampling volume is designed to assess the reliability of the treatment system product over time.

“The inclusion of NSF/ANSI 350, the American National Standard for water reuse treatment systems, in these important international plumbing and building codes is further recognition of the rigor of the NSF International standard and its effectiveness in helping these technologies gain use and acceptance in the marketplace,” said Jessica Evans, director of standards development at NSF International. “Water scarcity is a growing global issue and ensuring certified water reuse systems properly treat greywater will be an essential part of the solution.”

For more information about NSF International sustainability standards, or contact Jamie Bush at

Greywater Harvesting for Hotels

From Green Hotelier:

Harvesting greywater to reuse in toilets

Recycling greywater to use in toilets

Water stewardship is an extremely important aspect of good environmental practice for hotels. Many use reduced flow and flush in bathrooms, but how many are recycling water?

Water re-use is becoming core to many companies’ sustainability efforts and it’s never been more important.  Freshwater withdrawals have increased globally by about 1% per year since the 1980s (UN, 2016) and it is estimated that water scarcity now affects 40% of the global population (CAWMA, 2007).  Even in the UK some areas are reporting difficulties in meeting demand.

Hotels often do a lot to manage water consumption. Low flow taps and showers or aerators, reduced flush toilets or no flush urinals, sensor activation and good housekeeping practices all help to reduce the amount of water per guest, per room and per stay. But, even with these measures many guests admit to using much water during a hotel stay than they would at home, and in some water scarce areas, the difference in consumption between a hotel guest and the local population can be up to 20 times and dozens of litres.

Anything hotels can do to better manage their water consumption is a good thing, but how many look at recycling water?

Significant water consumption savings can be made from re-use initiatives. Rainwater harvesting can reduce mains water consumption by up to 30% whereas greywater recycling can save as much as 40%. Aside from lower metered water bills, companies can also benefit from reduced risks of storm water flooding, decreased sewerage charges and lower energy costs associated with water supply.

New water re-use solutions offer commercial organisations a variety of cost-efficient, reliable and highly effective options to help achieve their sustainability goals.  Claire Yeates, a Director at Waterscan said: “Many companies are aware of the benefits of water re-use but are naturally concerned about payback times and the potential operational impacts of installing new technologies. Add to this reliability issues from early-to-market systems and it’s easy to see why widescale uptake of water recycling has been hindered. We firmly believe that greywater recycling and rainwater harvesting can play a significant role in many company’s water strategies and that is why we are bringing new best-in-class technology to market.”

The various water recycling systems have been developed to give greater system design flexibility in line with customer priorities and requirements, plus a 30% faster return on investment. Waterscan systems now feature:

  • Multiple tiered redundancy to ensure complete integrity of supply.
  • Built-in telemetry which transmits system data and live diagnostics for preventative maintenance.
  • Siemens smart user interface for usage data and enhanced system monitoring.
  • Variable speed, load sharing pumps, insulation and slow close valves for an even quieter operation.
  • Low energy components so the system can produce 1m3 using just 1.5Kw/h energy.
  • A smaller system footprint which reduces installation costs and impact on building footprint.

Barry Millar, Operations Director at Waterscan, said, “Our new water re-use systems are now designed and largely built in the UK using modular components. This enables us to meet clients’ exact specifications in line with individual business strategies and site requirements. Our complete service involving design, supply installation and maintenance of water-saving systems, along with our consultative approach, gives us a unique ability to deliver optimum results across varied client property portfolios. All of this means that our clients will benefit from a faster return on investment and still have complete confidence in their operations.”

Greywater Recycling in Action at Premier Inn

In partnership with its client Premier Inn, Waterscan installed a greywater recycling system in water-scarce Abu Dhabi. The initiative is vastly reducing mains water consumption, saving an average of 735,000 litres (24%) of mains water each month – 60 litres per guest. Over the course of a year, this is the equivalent of 110,000 baths. 100% of toilet flushing at the hotel now uses recycled water.

Greywater Recycling

Greywater recycling captures the water used for showering or bathing and, after treatment through an ultra-filtration membrane system, is fed back into the property for non-potable purposes such as flushing toilets, irrigation and laundry.

  • Greywater Recycling Batch System: where low energy consumption is a priority and there is physical space for a larger system footprint, this low pressure filtration method takes a little longer but uses less energy in the process.
  • Greywater Recycling On-Demand System: where space saving and a faster return on investment are priorities, this high pressure approach delivers rapid ultrafiltration and therefore requires less tank storage and correspondingly reduced installation costs.

Rainwater Harvesting

Rainwater is collected, filtered and fed back into the property through a robust treatment system ensuring that only the cleanest water is utilised for non-potable purposes like vehicle washing, toilet flushing and irrigation.  A rainwater harvesting system is suitable for all commercial applications where there is adequate roof space to harvest sufficient water to achieve a good return on investment.

Hoteliers interested in learning more about water risk can read our Global Water Risk Assessment and find tips for taking action on water reduction in our manual Environmental Management for Hotels.

ITP members are acting on water on behalf of the industry by collaborating with member hotel groups to develop the Hotel Water Measurement Initiative. This universally recognised tool and metric will help all hotels of any size, anywhere in the world measure in a consistent manner. The HWMI is currently in the testing phase and will be released as a free tool for the industry in World Water Week at the end of August 2016.

(3BL Media/JustMeans) Water is not something that should ever be wasted. Just ask Californians who are suffering through their fifth year of drought. General Motors clearly understands that water conservation is essential as the company’s Detroit-Hamtramck Assembly plant, where the Chevrolet Volt is manufactured, now has a a rainwater capture system.

It took two years to complete the rainwater capture project which allows rainwater to be reused in manufacturing. The assembly plant, which is four million square feet, already had two rainwater retention ponds on its grounds, but it paid to send the excess water to the city’s treatment plant.

The fees it paid accounted for 14 percent of the assembly plant’s utility bill, so adding a third pond allowed the site to hold 47 million gallons of water, which is equivalent to a once in a 100 years storm event. The rainwater capture system allows GM to save $1.64 million a year while reducing its environmental impact. The rainwater project will pay for itself in a little over a year.

Rain comes into storm drains and then flows to the ponds. Floating pumps then transfer the captured rainwater to the plant’s power house and the power house treats the water with sand filters. The treated water is fed into the plant’s cooling towers, which reduces water use by 20 percent and saves $140,000 a year. The rest of the water is purified with carbon filters and reverse osmosis. Detroit Renewable Power plans to turn the water into steam to heat and cool the GM plant, plus 145 other Detroit area businesses. Any of the reject water from the purification process is used to help break down the paint sludge remaining from painting cars, which saves $75,000.

GM is committed to reducing water intensity by 15 percent by 2020 from a 2010 baseline at its global facilities. So far, GM has reduced water intensity by almost 10 percent over the past six years. The rainwater project at the Detroit-Hamtramck Assembly is one way that GM plans to meet its goal.
GM has other water saving projects in its facilities around the globe. In Joinville, Brazil GM uses reverse osmosis to filter water from recycled wastewater and use it for flushing toilets and industrial uses at its engine plant. It is the first automotive facility to use treated wastewater and saves the plant 22.9 million liters a year, equivalent to nine Olympic-sized swimming pools. GM has a number of water conservation projects at its two plants in Port Elizabeth, South Africa. The company held two full-day workshops with employees at the two South African plants and identified 7,360 kiloliters of water savings.
GM also works to protect watersheds with its watershed education program, called GM GREEN (Global Rivers Environmental Education Network). The 26 year-old program helps young people understand how they impact local watersheds. The program is the longest running conservation education program run by an automaker and reaches 150,000 young people. There are 50 facilities that are part of the program, including all of GM’s U.S. and Canadian manufacturing plants. GM now includes dealers in the program in order to spread awareness.

Photo:  GM


“When rainwater flows into the sewers, it turns into a flood. If you collect it, it becomes a resource.” This is the view of Makoto Murase – Japan’s rainwater collection pioneer.

For Makoto Murase, rainwater is a tremendous resource – and given the global scarcity we can’t afford to waste it.

In Tokyo in June the hot and humid Japanese summer emerges with the “tsuyu” – the first rainy season, which lasts about six weeks. The autumn rain (“akisame”), falling in September and October, marks the second rainy season. Between July and October and sometimes earlier, Tokyo – like the rest of Japan – is often hit by typhoons, which bring their share of rainfall and storms.

The problem is that the Japanese megalopolis is a densely packed and complex concrete jungle that isn’t always able to handle these heavy rains. Concrete is waterproof, which stops water being absorbed by the soil. Municipal sewers quickly overflow, causing heavy flooding. Tokyo city therefore needed a solution. And it was Makoto Murase who found it the early 1980s.

Makoto Murase was then employed in the wastewater department of the district of Sumida-ku, northeast of Tokyo. With the help of his team, he designed a system that collects rainwater from roofs, filters it through ingenious systems placed in the gutters, and then stores it in large underground tanks. At this point, it is not drinkable but can be used to water green spaces, flush toilets, run washing machines, and extinguish fires. Although Makoto Murase is not the only one who has thought of a rainwater collection system, he was the first to design it on an urban scale.

Meanwhile, Sumida-ku was preparing to become home to largest sumo stadium in Tokyo, the famous Ryōgoku Kokugikan. Makoto Murase saw the perfect opportunity to test his idea. After a first refusal from his bosses, he managed to convince Japan’s conservative Sumo Wrestling Federation of the project’s economic viability. The project proved to be such a success that it profoundly changed the way urban planners, engineers and architects design buildings.

The system invented by Makoto Murase, now nicknamed “Dr. Skywater”, has many advantages: it limits the impact of floods, it achieves significant water and energy savings, it offers the municipality a widely available and “green” reserve of water that it can use in a multitude of ways, and finally, it helps to change perceptions about rainwater. Makoto Murase views this “sky water” as a tremendous resource – and given the global scarcity we can’t afford to waste it.

With this conviction, Makoto Murase now travels Japan – and the world – taking his model to other cities, such as Bangladesh where he participated in the Amamizu project. In 1995, Sumida-ku, followed by Tokyo, made it obligatory to construct underground rainwater tanks for every new building.

The author of several publications, including the Rain Encyclopedia, Makoto Murase is now head of an organization that promotes relatively simple and inexpensive sustainable technology which according to him, could help to solve the water crisis.

No, California’s drought isn’t over. Here’s why easing the drought rules would be a big mistake

Folsom Lake, Calif.After months of El Niño rainfall, Folsom Lake became so full that excess water was being released over Folsom Dam, above. But reservoirs in Central and Southern California remain well below their averages. (Brian van der Brug / Los Angeles Times)

By Michael Hiltzik Contact Reporter LA Times

4 April 2016

On March 23, the San Juan Water District, which serves upper-crust residential estates in the Sacramento area, declared that the drought is over.

After months of El Niño rainfall, Folsom Lake, the district’s chief water source, had become so full that excess water was being released over Folsom Dam. “That was a very visible signal,” says Lisa Brown, customer service manager for the district. Customers, some of whom own spreads as large as 10 acres, “wanted to know why they were still being held to drought restrictions.” So the district board lifted them, replacing a 33% mandatory conservation cutback with a 10% voluntary cut and eliminating a 10% drought surcharge on water rates, effective April 1.

The abundance of water, says Assistant General Manager Keith Durkin, made it “very difficult to defend a continued 33% reduction in use.”  Across Northern and Central California, brimming reservoirs and a recovering mountain snowpack are prompting water users to pressure Gov. Jerry Brown and the State Water Resources Control Board to ratchet back restrictions that have made California a national leader in conservation.

The Placer County Water Agency on March 18 asked state authorities to rescind emergency drought regulations on the grounds that its supply is “robust enough to meet demand” from its customers through 2017. The Nevada Irrigation District, east of Marysville, cited “well above average precipitation, full reservoirs and a mountain snowpack” in rescinding its own drought declaration and calling on the state to ease its restrictions.

Presentation8Districts such as San Juan have taken matters into their own hands by unilaterally removing the most stringent regulations on their own customers. San Juan says its customers met their conservation obligation by reducing usage by 34% from June through February. Not all the protesting districts managed that; the Georgetown Divide Public Utility District in El Dorado County, which last month lifted a drought-inspired moratorium on new water connections, acknowledges that it was upbraided by the state board in January for failing to meet its goal.

The Water Resources Board is looking for ways to ease pressure on water-rich districts without giving them a free hand. It has scheduled to consider relaxing some restrictions at a meeting in May, following a workshop at which those districts will be asked to make the case for more flexibility. “In the eyes of Placer County and San Juan the job is over,” says George Kostyrko, a spokesman for the board. But water conservation “isn’t a regional or a siloed issue,” he says. “It’s a statewide issue.”

Policymakers are getting the uneasy feeling that public impressions of newfound abundance could undo much of the progress of the last few years. “Droughts are really a matter of signals,” Jeanine Jones, deputy drought manager for the California Department of Water Resources, told me. “When it has rained a lot, people get comfortable.”

That would be a mistake. Experts reckon that even if 2016 represents a break from the record dry conditions of the last four years, the damage done by the drought to the state’s water supply will be lasting. Long-term reserves in groundwater have been drained to the point that years, even decades, of wet weather would be required to replenish them. “We’ve depleted our savings account in reserves and groundwater storage,” Jones says.

A more likely scenario for the future is a change in climatic conditions requiring a permanent change in water usage habits. “In the water community, people talk about a new normal, with dry conditions becoming more frequent and more lasting,” says Matt Heberger, senior research associate at the Pacific Institute, an environmental think tank in Oakland.

These conditions create a quandary for policymakers, who must tread a fine line between enforcing restrictions that people may feel are no longer necessary while guiding residents, growers and businesses toward enduring changes in usage patterns. “Messaging is important,” says Ellen Hanak, a water expert at the Public Policy Institute of California. “It doesn’t make sense to tell people conditions are terrible when they’re not, but it makes sense to tell them that the precipitation we’ve gotten hasn’t put us in a safe spot.”

RELATED: Californians fall a bit short of Brown’s call for 25% cut in water use after 9 months of conservation

The habits born in the last few years, if they take root, could produce lasting gains in water sufficiency for the future. The emergency atmosphere of the last couple of years has a lot to do with that: In the same sense that $3-a-gallon gas starts turning people off gas-guzzling SUVs, the best weapon against water shortages in the future is a sensation of crisis today.

Since January 2014, when Gov. Brown declared a drought emergency, Californians have met the challenge. They’ve replaced tens of millions of square feet of turf with drought-tolerant landscaping (coaxed by hundreds of millions of dollars in utility rebates) and installed water-thrifty indoor fixtures. The results are remarkable: Statewide average residential consumption of 61 gallons a day in January was nearly 15% below the same month a year earlier. Last summer’s usage was more than 23% lower than a year earlier.

Indications abound that the regional drought is far from over. The water level of Lake Mead, the reservoir behind Hoover Dam that stores Southern California’s Colorado River supply, stood last week at 1,081.32 feet above sea level — a recovery of about 6 feet since it reached a recent low point in June. But that’s still the lake’s lowest level in any March since 1937, when it was still filling for the first time. Mead is currently at about 39% of capacity.

Although three major Northern California reservoirs — Shasta, Lake Oroville and Folsom Lake — are currently above their average historical levels, they’re the exceptions, according to the Department of Water Resources.

Reservoirs in Central and Southern California remain well below their averages, with Don Pedro Reservoir in the Sierra foothills at 82% of its average and 60% of capacity, and Perris Lake in Riverside County at 43% of its average and 36% of capacity. While the snowpack is calculated at 87% of normal overall, its depth varies widely across the state — rising over recent months to roughly 100% of the average in the far north of the state, but reaching only about 75% of the average toward the south. The U.S. Drought Monitor still shows much of Southern and Central California to be facing long-term “exceptional drought.”

The problem with giving some parts of the state a pass on water rules while maintaining them elsewhere is that California’s water supply system binds north and south together. The long-term water crisis can only be solved as a statewide effort.

The state has begun to make changes that may well be lasting. “There will be a different-looking outdoor space 10 or 20 years from now than there was 10 or 20 years ago,” Hanak says. But the mind-set producing those changes could be fragile. The message needs to be that “the fact that we’re easing up doesn’t mean we’re out of drought mode.”

Keep up to date with Michael Hiltzik. Follow @hiltzikm on Twitter, see his Facebook page, or email


Jump DiagramIn another post we showed how to size a PURAIN self cleaning Jump Filter.  In this post we show that once you have selected a filter, how to estimate the expected capture efficiency.

As reference, please check out our post on sizing.  Here is a summary:

  1.  Look up the 5 minute intensity, 1 year interval rainfall for your installation site on the NOAA website.  Using this number to calculate flow off the roof.
  2. Compare this flow to the maximum allowable flow for each filter and choose the smallest filter that will handle this flow.Fosse Process Flow Oct [Autosaved]


Download this handy sizing chart!  It shows recommended sizing for a wide number of US cities using the method above.

The message is that it is not possible to give a blanket square footage rating for a filter because rainfall intensity varies so widely throughout the US and throughout the world.  Many other filter manufacturers erroneously give roof square footage ratings based on intensity rainfall rates in Germany!  There are places in the US and elsewhere in which these guidelines work, but there are many more that do not.

Once you have selected a PURAIN filter, you can estimate how much water it will collect.  To do this, I take a 9,000 square foot small commercial roof and place it in 3 separate locations, Boston, Miami, and San Francisco.

Based on 1 year, 5 minute intensities, the following PURAIN filters are recommended:

Boston – PURAIN DN 200 8″ Inlet Filter

San Francisco – PURAIN DN150-S 6″ Inlet Filter

Miami – PURAIN DN300 12″ Inlet Filter

There you have it, different filter sizes are recommended in different location even though the roof size is exactly the same.  It tends to rain harder in Miami than in Boston and harder in Boston than in San Francisco.  This means you need a different sized filter for each location.  So, how does each filter perform?

To figure this out, we use actual 5 minute rainfall data over the course of a year.  I chose near average years for each city which turned out to be 2014 for Boston and Miami and 2015 for San Francisco.  There are actually over 106,000 data points in a single year so the spreadsheet gets a little cumbersome.  Nevertheless, there “only” a few thousand five minute periods in any of these 3 locations in which it actually rained, so that cuts it down a bit.  If flow rate in any 5 minute period exceeds what the filter screen can accept, then a portion is rejected in a hydraulic jump.  We simnply add up all the water that is captured and all the water is rejected to figure out capture efficiency.  The website used for this is in this link if anyone wants to check it out.  there is data from all over the US.  A nice guy at NOAA showed me how to extract the data.



  1.  Capture efficiency is very good for all 3 locations.
  2. There are a decent number of hydraulic jumps for all locations.  Miami,  especially, has a lof of filter cleaning with 24 hydraulic jump events.
  3. More water is captured in Boston than in Miami even though it rained less there. This is due to the high intensity rains in Miami.  Indeed, around 75% of the rain in Boston in 2014 was at a rainfall rate of 0.5″ per hour or less versus only 28% for Miami.



The results raise a few questions:

  1.  What if smaller filters were used in Boston and San Francisco?
  2. What if a bigger filter were used in Miami

Inquiring minds want to know, so here are the results:



  1. Not much capturee efficiency is lost in Boston, so downsizing may be OK.  However, overall hydraulic load on the filter will be exceeded more frequently so an emergency bypass would be required.
  2. In Miami, the bigger filtercaptures a little more water but the number of hydraulic jumps decreases a lot so the filter may not stay as clean.  The added cost of the bigger filter may not be warranted.
  3. In San Francisco, capture efficiency drops a lot and the 4″ filter is too small.  Plus overall maximum flow would be exceeded too often




  1.  The approach of using 1 year, 5 minute interval data as a sizing guide works well for the cities investigated.  we have found this approach to work well in many other geographies as well.
  2. Capture efficiency is good for the filters selected using this method and trying other sizes probably would give worse results.



Drexel University: Here’s Why We Should Use Rainwater to Flush Toilets

From the Drexel University press release:

Rain Barrel. Source:

Rain Barrel. Source:

If you live in one of four major U.S. cities chances are you’re letting the benefits of a ubiquitous natural resource go right down the drain — when it could be used to cut down your water bill. Research by a team of Drexel University environmental engineers indicates that it rains enough in Philadelphia, New York, Seattle and Chicago that if homeowners had a way to collect and store the rain falling on their roofs, they could flush their toilets often without having to use a drop of municipal water.

Toilet flushing is the biggest use of water in households in the United States and the United Kingdom, accounting for nearly one-third of potable water use. But there is no reason that clean, treated, municipal water needs to be used to flush a toilet — rainwater could do the job just as well.

“People have been catching and using rain water for ages, but it’s only been in the last 20-30 years that we have realized that this is something that could be done systematically in certain urban areas to ease all different kinds of stresses on watersheds; potable water treatment and distribution systems; and urban drainage infrastructure,” said Franco Montalto, P.E., PhD, an associate professor in Drexel’s College of Engineering, and director of its Sustainable Water Resource Engineering Lab, who led the research effort. “The study looks at four of the largest metropolitan areas in the country to see if it rains enough to make implementation feasible and, if everyone did it, what effect it would have on domestic water demand and stormwater runoff generation in those cities.”

The process of collecting and using roof runoff, which researchers call rainwater harvesting, has been working its way into vogue among urban planners and water managers over the last couple decades and has been implemented widely in California in the wake of its water crisis. This study, which started as the graduate thesis of Drexel alumnus Nathan Rostad, was recently published in the journal Resources, Conservation and Recycling, and is one of the first to crunch the numbers and sort out just how feasible, and beneficial, it would be as a way of offsetting potable water use for non-potable purposes while at the same time reducing generation of undesirable urban stormwater runoff.

“When the natural landscape is replaced by a building, rain can no longer infiltrate into the ground,” Montalto said. “It runs off, is captured in drains, where it can cause downstream flooding, carry pollutants that settle out of the air into local water bodies or — in the case of a city like Philadelphia or New York — cause the sewer to overflow, which leads to a discharge of untreated wastewater into local streams and rivers. So capturing rainwater can help to reduce the demands on the water treatment system and ensure that it will still function properly even during heavy rainfall events.”

Rainwater Harvesting Tank. By SuSanA Secretariat, Source:

Rainwater Harvesting Tank. By SuSanA Secretariat, Source:

Taking into consideration the cities’ annual rainfall patterns, residential population and roof areas, the team calculated that, with enough water storage capacity — a little more than a standard 1,000-gallon home storage tank — a three person family in a home with the city’s average roof size would have enough water to cover over 80 percent of its flushes throughout the year simply by diverting their downspouts to collect stormwater.

This would reduce overall household potable water demand by approximately 25 percent, which could mean slashing the municipal water bill for an average-sized home by as much as one-fourth. But even without installing a storage tank capable of holding a year’s worth of flushing water, a scaled-back version would still help chip away at the water bill.

“In general, greater potable water savings are estimated in cities with either larger roof areas or lower population density. However, such savings would be accompanied by smaller reductions in runoff,” the authors write. “Philadelphia and Seattle are the two cities where percent water savings would be greatest if residential neighborhoods were all equipped with rainwater harvesting systems.”

From a stormwater management perspective, an average residence with a 1,000-gallon rainwater harvesting system could reduce runoff by over 40 percent, according to the study. Obviously this would vary by residence — with the size of the water storage container and the water demand for toilet flushing — but as a whole, cities could see a significant reduction in the amount of stormwater their infrastructure would have to handle during each storm.

Among the cities studied, Philadelphia would see the largest percentage of runoff reduction if rainwater-harvesting systems were installed in residences citywide. This is because the average roof size in Philadelphia is the smallest of the cities surveyed, so there is less runoff to manage from a single roof. The researchers found that larger percentages in runoff reduction from a rainwater harvesting system can be the result of either small roof sizes or high population densities. But managing stormwater is a concern for all urban areas.

“Think of it this way. Before the building was on the site, the rain was intercepted by vegetation canopies, and/or infiltrated into natural soils. Either way, the rain ended up replenishing soil moisture, allowing the plants to grow, and recharging the local groundwater aquifer,” Montalto said. “The more buildings that go up, the more we need to consider how to manage the water that would have landed in the drainage area they’re displacing.”

Stormwater recycling programs are already being offered by water departments in urban areas across the U.S., including Philadelphia. For more information about stormwater recycling in your area visit: