October 19, 2014
By Mike Gipson and John W. Lauer
The use of high-efficiency toilets (HETs) and high-efficiency urinals (HEUs) is becoming common practice in the development of many current commercial projects. While HETs and HEUs are now mandated by codes in many states and municipalities,1 engineers and specifiers are also choosing these water-saving products to meet green building criteria such as Leadership in Energy and Environmental Design (LEED) and to reduce operating costs that are being impacted by rising water rates.
An HET must have a maximum single-flush discharge of 4.84 Lpf (1.28 gpf) or a maximum dual-flush of 6/4.84 Lpf (1.6/1.28 gpf) to achieve a minimum 20 per cent savings over the 6-Lpf (1.6-gpf) toilets that have been in use for the past two decades. An HEU must have a maximum flush of 1.9 Lpf (0.5 gpf), though there are also models available with 0.9 Lpf (0.25 gpf) and 0.5 Lpf (0.125 gpf). These HEUs, as well as waterfree urinals, offer considerable water savings over the 3.8-Lpf (1-gpf) urinals that have been the industry standard.
In new construction, designing HETs and HEUs into the plumbing system is relatively clear cut. The water supply system and the drainage pipes can be designed to accommodate the products’ higher operating pressures and reduced flows. This gives specifiers a bit more leeway in product choice. However, incorporating such high-efficiency fixtures in a building retrofit or a remodel often requires greater consideration of the existing conditions and capacities of the drainage and supply systems.
Aging infrastructure can impact the performance of water-efficient plumbing products, and as a result, the specification of water-efficient products is not as simple. When dealing with an older plumbing system, there are important factors that must be taken into account by the specifier to ensure use of lower-flushing valves and fixtures will not have an impact on system performance, negating the benefit of the water savings.
This article reviews considerations that can help the specifier avoid potential performance issues. Putting them into focus enables the team to deal with the variables that emerge when matching newer high-performance plumbing products and systems with older structures. Water conservation is still possible in older buildings. However, accommodation must be made for factors such as bowl performance, drainage, and water supply—all of which directly impact the goals of water conservation.
An older building’s drainline condition should be a primary concern when considering use of high-efficiency plumbing equipment and systems. Older buildings constructed at a time when toilets flushed at 13.25 Lpf (3.5 gpf) or higher have drainlines designed to effectively move waste with higher volumes of water. Even buildings where 6-Lpf (1.6-gpf) water closets have been installed may have larger-diameter drainline piping than what is recommend for HETs.
Besides having larger diameters, the drainlines in some older buildings may have sag or slope interruption, have too little slope, or have buildup in the pipe that has occurred over time. When these conditions exist, the reduction in water flow in the pipes that will occur when lowering the flush from 13.25 L (3.5 gal)—or even 6 L (1.6 gal) to 4.84 L (1.28 gal)—can result in more frequent clogging of the drainlines.
The recent Plumbing Efficiency Research Coalition (PERC) study, “Drainline Transport of Solid Waste in Buildings,” examined this problem of transporting waste in older drainlines with high-efficiency toilets.2 The study was conducted by International Association of Plumbing and Mechanical Officials (IAPMO), International Code Council (ICC), American Society of Plumbing Engineers (ASPE), Plumbing–Heating–Cooling Contractors Association (PHCC), Alliance for Water Efficiency (AWE), and Plumbing Manufacturers International (PMI).
One of the issues the PERC study targeted was concern over the efficacy of drainline transport when flush volumes drop below 4.84 L (1.28 gal) of water. The testing indicated these lower flows produced flush volumes below 4.84 L, contributing to an increase in the number of clogs and blockages in drainlines. Additional findings of the study include the impact of toilet paper and other factors, which impact drainline performance. Additionally, PERC has just announced funding has been secured for Phase 2 of the study, and more information will be coming out soon.3
When replacing older, higher-flushing toilets, many buildings will often hydro-jet the drainlines before upgrading to HET fixtures. This can remove the buildup that has occurred in the drainlines over time. Clean drainlines will help ensure waste transport with the lower flushing volumes. Once the HETs are installed, many facilities will then hydro-jet the drainlines on a regular basis for preventive maintenance.
If there is a concern about the efficacy of an existing drainline, it often recommended to upgrade one restroom with high-efficiency fixtures and flushometers as a test, and then evaluate the system performance for a period to see if there are any adverse effects on the drainline carry before changing the whole building’s systems.
In a building where there may be drainage concerns, using a 6/4.2-Lpf (1.6/1.1-gpf) dual-flush instead of a 4.84-Lpf (1.28-gpf) single-flush is often a viable solution. The 6/4.2-Lpf dual-flush is recognized in most codes as a high-efficiency flushing device, equivalent to a 4.84-Lpf single-flush. The additional water delivered for the full flush (i.e. ‘solids’ flush) is often enough to overcome these adverse conditions in the old drainage system. The reduced ‘liquid’ flush offsets the extra water used for the solid flush, particularly as ‘liquid’ flushing (often with light solids like toilet paper) typically occurs twice as often as a ‘solids’ flush.
Building designers and specifiers should also consider the placement of other water-consuming fixtures (e.g. lavatories and flushing urinals) upstream of the HETs to put more aggregate flow through the pipes. Additionally, drainline slopes of less than 6.35 mm per 0.3 m (¼ in. per ft) should be avoided when using HETs. If there are concerns with the supply or drainage, then it is in the best interest to engage a plumbing engineer to evaluate and ensure the system is capable of performing adequately on the reduced flows.
On the water supply side, another important consideration for the specifier considering a change to high-efficiency fixtures is to ensure the building has adequate water pressure and flow. This is particularly important when using flushometer water closets. The operating parameters for high-efficiency fixtures are much more critical than for older fixtures, which had plenty of excess water to work with.
While high-efficiency valves and bowls use less water, the amount of energy behind the water is much more critical in a high-efficiency design. Most 4.84-Lpf (1.28-gpf) toilets require at least 172.37 kPa (25 psi) of running (flowing) pressure to ensure proper evacuation—some fixture manufacturers may require even higher minimum flowing pressures. This is significant as older 13.25 L (3.5 gal) per flush bowls often would perform down to 103.42 kPa (15 psi). The supply pipe sizing in the building should be adequate to supply water to the flushometer and bowl at a rate of 94.6 L/per minute (25 gal/per minute) at this minimum 25-psi flowing pressure. If a building has lower operating pressures, restricted pipes or an overall weak plumbing system, this can result in poor performance of the 4.84-Lpf bowls. Steps should be taken to improve the water supply to the valves and fixtures before changing the fixtures and valves out.
Bowl and flushometer valve performance
Most HETs are tested and certified to meet the highest Maximum Performance (MaP) testing score of 1000 grams when flushed with 4.84 L (1.28 gal). When the discharge is reduced, MaP scores in turn typically decrease.
While lower scores may be acceptable for residential use, decreased performance in commercial applications—where greater amounts of paper and other materials are often disposed of in the bowl—could lead to greater user complaints and a higher level of maintenance. Potential water savings can evaporate quickly under these circumstances.
When a restroom is retrofitted to 4.84-Lpf (1.28-gpf) toilets, it is also recommended to change the complete flushometer valve. Since the diaphragm kits and pistons in older flushometers are interchangeable, many building owners try to save in the change-out by just replacing the diaphragm kit or piston. It should be noted, the fixture always needs to be changed; a bowl designed to flush on 13.25 L (3.5 gal) simply will not flush properly when reduced to 6.0 or 4.84 Lpf (1.6 or 1.28 gpf). While older flushometer valves are designed to last many years and can be easily maintained with modern replacement kits, the valves themselves were not designed and manufactured to the exacting tolerances required in today’s high-efficiency models.
Additionally, the wear and buildup that occurs in an older valve body over time, as well as in the stop and handle assemblies, can also impede performance at the reduced flushing levels. To ensure proper bowl, valve, and system performance, the complete valve should therefore be replaced with a new high-efficiency model. Additionally, the older equipment is often recyclable, making the decision further environmentally responsible.
Another consideration when changing to high-efficiency fixtures is the rough-in and fixture dimensions of the existing and new fixtures. When switching out older water closets and urinals, there may be differences in the rim height, spud location, and flange thicknesses from one model to another. Even high-efficiency fixtures offered by the same manufacturer may have differences from the fixtures that manufacturers developed years ago.
Retrofits typically rely on installing new fixtures on the old fixtures’ existing outlet flanges since it is costly and difficult to move the flanges. When doing this, there may be dimensional changes impacting esthetics and practicality because fixtures’ outlet-to-rim-dimension varies among manufacturers, as well as from model-to-model. These dimensional differences are allowable within the tolerances set in American Society of Mechanical Engineers (ASME) A112.19.2/Canadian Standards Association (CSA) B45.1, Ceramic Plumbing Fixtures. Installing a new urinal fixture on the same outlet flange of an older fixture, however, may mean the rim is higher. This could make a urinal fixture, for instance, non-compliant with Americans with Disabilities Act (ADA), which calls for a urinal rim height maximum of 432 mm (17 in.). This standard is harmonized with Canadian Standards Association (CSA) B45.1, Ceramic Plumbing Fixtures.
Installing new fixtures in place of older models may also expose old caulk lines that need to be removed. Repainting or retiling parts of the mounting area that were previously hidden may be necessary as well. One solution is to choose larger footprint urinal fixtures, designed specifically for retrofit applications, which conceal old holes and markings.
For all types of commercial projects, today’s options and necessary decisions are dramatically different from even as recently as 20 years ago. The plumbing landscape is more complex, yet full of new approaches and technologies to reduce water usage and operating costs, while increasing efficiencies.
Considerable groundwork will ensure these systems meet the specifier’s performance expectations while driving requirements to save water. The underlying criteria are to use caution and due diligence when specifying HET fixtures in older infrastructure sites. That means taking into consideration the physical conditions of the entire plumbing system, and not just the fixtures themselves. The water supply, drainline, and particular characteristics of these new fixtures’ performance are more important when water conservation is the objective.
1 For more information, visit www.iapmo.org/Official%20Articles/2008-01%20CA%20First%20with%20HETs%20and%20HEUs.pdf and www.santacruzsentinel.com/santacruz/ci_24267965/capitola-targets-obsolete-toilets-new-standard-1-28. (back to top)
2 For more, visit www.plumbingefficiencyresearchcoalition.org/projects/drainline-transport-of-solid-waste-in-buildings. (back to top)
3 Visit www.plumbingefficiencyresearchcoalition.org/wp-content/uploads/2012/12/Drainline-Transport-Study-PhaseOne.pdf. (back to top)
Mike Gipson has been product line manager of flushometers at Sloan Valve Company for three years. He has more than three decades of product management and marketing experience. Gipson graduated from Augustana College and earned his MBA from The University of Illinois. He can be reached at firstname.lastname@example.org.
John Lauer is Sloan’s western region director of sales, and has had a varied career with the company including a mix of technical, sales, and supply chain positions since he joined in 1984. He has served on many technical committees that developed the first performance requirements for water-efficient plumbing products. Lauer has been an active participant in the Plumbing Manufacturers Institute (PMI), a trade association for plumbing manufacturers, and was president of the organization in 2005. He has a bachelor’s degree in product design and development from Southern Illinois University and an MBA from Roosevelt University in Chicago. Lauer can be reached at email@example.com.
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