Gray matters; Water reuse systems

Gray-water reuse systems are becoming a staple in both newly constructed and existing facilities. Industry experts share the benefits and pitfalls of specifying and implementing the systems.

By Jenni Spinner, Contributing Editor October 15, 2010

Our Roundtable Participants (from left)

  • Steve Bilson, CEO, ReWater Systems Inc., Newbury Park, Calif.
  • Lloyd Ramsey, CET, CEM, LEED AP, Senior Principal, Stantec Consulting, Phoenix
  • Rob Zimmerman, LEED AP, Manager, Engineering, Water Conservation and Sustainability, Kohler Co., Kohler, Wis.

CSE: Have you designed gray water reuse systems into commercial buildings recently? Describe the design.

Lloyd Ramsey: Our engineers provided design support to a green community in British Columbia called Dockside Green, a 1.3 million sq-ft community built on a brownfield site in Victoria, British Columbia. Our mechanical and electrical design challenges included reduced water and energy usage, improved occupant comfort, and reduced light pollution. Design and efficiency features included a 65% reduction in indoor water use with dual-flush toilets, low-flow fixtures, and use of gray water for sewage conveyance while treating 100% of the site’s wastewater in a campus-wide plant, which reuses it in central water features, toilet flushing, and on-site irrigation. Water reuse was at the forefront of the design, and the project spanned several building types, earning the project the highest sustainability rating for a new construction project ever awarded by the Canada Green Building Council (CaGBC).

Steve Bilson: Whether it’s for a military barracks, or an apartment building, or a laundromat in the middle of a strip mall, all of our systems use the same philosophy of reusing gray water for irrigation as it’s produced, not storing it. Storing causes all sorts of problems because gray water has the ability to breed algae and other slimy stuff that can clog filters and downstream irrigation components. Larger potential surges require larger tanks, pumps, and filters and—on the irrigation side—larger pipes, valves, and irrigation fields. All our systems have our unique irrigation controller similar to what irrigation maintenance personnel are used to dealing with. These are irrigation systems, in the final analyses.

CSE: What percentage of clients request gray water and/or rainwater collection systems for their buildings? Why do they request them?

Bilson: Judging on the volume of buildings that get built without reusing their gray water, a very small percentage of overall projects request gray water irrigation systems. This is usually because the people in charge of the project view water reuse as irrelevant to the building. Those people are rarely the ones paying for the building after it’s built, or maintaining the building, and thus will never see the water and wastewater bills and don’t care about that aspect of the building’s life. That perspective is extremely myopic and a perfect case of bad value engineering, but it’s the norm.

Ramsey: There’s a much higher interest in harvesting rainwater, as approximately 75% of our current [U.S. Green Building Council (USGBC)] LEED projects capture that feature. There is a significantly lower percentage of clients inquiring about gray water system design. As a strategy, it’s not been universally accepted because of limitations on code authority. More importantly, there are misconceptions—ones we continually try to correct—that these strategies translate into added costs.

CSE: What types of rebates or incentives are there to include water conservation systems in buildings?

Ramsey: Rebates, requirements, and incentives are still largely decided by regional agencies, and there haven’t been many developments with black or gray water reuse rebates. In the U.S., there are several states—such as California—which are requiring increased water efficiency in buildings and developers need to consider gray water reuse to stay compliant. Most agencies develop standards based on percentages of efficiency, comparative to building code.

Bilson: It depends on the jurisdiction the project sits in. In California, almost all the commercial incentives come from the wastewater side, and they almost don’t have to be requested because they’re already built into the sewer rate structure. Usually it’s just a matter of documenting the system’s performance, usually with a meter. On residential projects, almost all incentives come from water conservation, and they almost always have to be requested from the agency. The WaterSmart program goes a ways toward solving that problem, though gray water reuse is only now coming into its right in that program.

Rob Zimmerman: Many of the water-saving plumbing products and appliances are price-competitive with less efficient models; therefore, savings in reduced water and energy bills are direct benefits. In addition, many water utilities offer rebates or other incentives for water efficiency projects to help offset retrofit costs in existing buildings. Learn what’s available in your area.

CSE: When using gray water or rainwater in HVAC systems, kitchens, and restrooms, what code issues do you have to tackle?

Ramsey: As a whole, many codes have been quiet on the subject, lacking specificity on performance requirements. Consequently, local agencies are establishing and enforcing regional standards. The most challenging code issues arise with client strategies to reuse the water, how they intend to repurpose it. Some uses require potable standards while others may not.

Bilson: The code for gray water reuse in restrooms just became available in California, but the industry here is still awaiting some large company to invest in a standard for the systems to be tested against. NSF 41 looks like it will become a testing standard soon, and that, along with California and other states’ various construction codes, will allow for simpler permitting.

Zimmerman: Use of nonpotable water (gray water, rainwater, or municipally supplied reclaimed wastewater) is controlled by local plumbing and mechanical codes. It’s important that when considering use of nonpotable water, engineers work with knowledgeable trade professionals who understand what is and is not allowed, and how to install systems safely. Codes and standards for nonpotable water systems are changing and being adopted in more cities and states as the need for reuse of water increases.

CSE: What other tactics are you using to maximize water conservation?

Bilson: On top of the advantages of water reuse such as wastewater reduction and decreased energy demand, a legal gray-water irrigation system usually requires underground drip irrigation, which is 30% to 60% more efficient than sprinklers.

Ramsey: We’re continuously using a larger variety water of reduction technologies. Low-flow toilets and water-efficient sinks and showerheads are becoming more of a staple rather than a specialty item. As a whole, buildings engineers try to avoid evaporative-type air conditioning systems to provide more sustainable options.

CSE: What are the traditional products or systems used by plumbing engineers to obtain LEED points or other green credits?

Zimmerman: The easiest and most common way to earn water efficiency points in LEED and in other green building rating systems is to use high-efficiency plumbing products, including 1.28 gal./flush (gpf) toilets, 0.5 gpf urinals, and low-flow bathroom faucets and showerheads. EPA’s WaterSense program has specifications for all these products that provide assurance of water efficiency and great performance. Other strategies include use of low-water-demand landscapes, rainwater capture for landscape irrigation, monitoring of water use by cooling towers, and use of ENERGY STAR rated commercial clothes washers and dishwashers.

CSE: What tactics do you suggest engineers use to maximize water conservation?

Zimmerman: The first thing to do is understand where the opportunities lie. Perform a water audit on the building, or hire a performance contracting company to help.

CSE: What are some of the unforeseen problems with gray water systems you’ve encountered?

Ramsey: When the industry was first exploring gray water systems, we commonly saw problems with the levels and quality of water treatment. Foaming was common. Both our understanding and the resources have evolved; we’ve learned how to accommodate these issues with different measures and strategies.

Bilson: Keeping landscapers and other contractors from tearing up the underground irrigation portion of the system after construction is completed. The standard contractor mentality is to try to hide whatever they did wrong, but the truth always comes out in the end. It’s a big pain to have to prove what happened. The easiest way to deal with this problem is to include in any contract for work around the grounds a clause that says there is underground drip irrigation on the premises and any damage to it will result in the damager having to repair the damage. Simply knowing they can’t go ripping through the landscape keeps them from doing so.

CSE: What are some of the unanticipated benefits you or your clients might have encountered?

Bilson: They are usually surprised at the lower cost for irrigation system maintenance due to the entire irrigation system being buried underground. Broken sprinkler heads are a huge payout both in repairs and water bills for normal irrigation systems. With underground irrigation, all of that is gone. It’s hard to quantify that value upfront for the client, but it’s a noticeably real factor for those who have managed landscapes and paid for irrigation repairs on other projects.

Ramsey: The engagement of building users has been deeper and more profound than anyone could have foreseen. Company or business owners with office space that use gray water systems have recognized a workforce morale value in being able to showcase and provide a workplace that uses sustainable practices.

CSE: What water management strategies aren’t working as well as originally thought, or promised?

Bilson: Most of the large companies that manufacture the weather-sensitive “evapo-transpiration” (ET) irrigation controllers actually bought an old technology that doesn’t work very well or at all. Those controllers use input signals that the client has to pay for, old logic that wasn’t so smart, and generally are highly overrated, yet those large irrigation companies are selling that old stuff like it was state-of-the-art. The results are disenfranchising the consumer to an otherwise sound concept. The newer small companies have great ET controllers.

Ramsey: As these systems have evolved, landscaping strategies have changed to better accommodate the water reuse capabilities these systems provide. Tropical plants, for example, required often more water than these systems could generate. Water-efficient plants and xeriscaping strategies have since made this issue a moot point. Other challenges typically arose in public bathrooms using low-flow technology, and odor control was an initial issue which needed to be addressed over time.

Zimmerman: We are concerned that toilets that are designed to use a certain flush volume are being retrofitted to use less water. While this may work in some applications, toilets will perform best at their rated flush volumes. Poor toilet performance leads to double-flushes, which cancel out any water savings. The most reliable option is to replace toilet bowls and flushometers with models that are compatible and designed to work together.

CSE: Where do you think the trend is moving for water conservation in the future?

Ramsey: Throughout North America and the world, there is increased pressure to increase water efficiency in buildings. The measures that are codified now will only be tightened, by regulators and by society.

Zimmerman: It’s clear that we all need to use water more efficiently, both in commercial buildings and at home. There are many new water-saving products available that save water while delivering improved performance. Many more are being developed. Use of nonpotable water is growing rapidly already, and will grow even more as codes and standards are developed and adopted.

Bilson: On-site water recycling is definitely coming of age. Gray water irrigation has already arrived.

CSE: Are gray water reuse systems something that engineers should be pushing harder? Why or why not?

Bilson: In areas that irrigate year-round, like the arid Southwest, they should absolutely be pushing gray water irrigation systems harder. The cost/benefit ratio is so good that few owners/principles in those geographical areas have problems with the concept. The return on investment is so high that it is a selling feature even if the project will be immediately resold. Engineers really just need to know which companies provide good gray water irrigation systems for their suggestions to be welcomed with open arms.

CSE: Anything to add?

Zimmerman: Engineers need to stay up to date on the latest technologies. There are many educational resources available, starting with those from the American Society of Plumbing Engineers (ASPE). Existing buildings represent a significant portion of society’s demand for water and energy. Building engineers and facility managers have a critical role to play in helping us reduce this demand.

Ramsey: Client and industry education is still one of biggest priorities and challenges with gray water systems. The immediate interest with buildings engineering is in energy efficiency and with conserving nonrenewable resources like power and gas. We tend not to look at water as a nonrenewable resource, and we should. Depending on geography, there’s also not as much incentive to be water efficient as there is to be energy efficient.  Power and gas are crucial parts of sustainable design but, holistically, fresh water consumption and gray water reuse also need to continue as growing as parts of the discussion.