According to the 1999 AWWARF Residential End Uses of Water Study (REUWS), showers are the 3rd largest water use in the North American home. (As you can see below, only toilets and clothes washers are larger.)
According to the same study, the average North American shower lasts for about 8 minutes with an average flow rate of 2.1 gallons per minute-gpm (7.9 litres per minute-Lpm) (REUWS, 1999).
Two components of water use in a shower are flow rate and duration. The National Energy Policy Act of 1992 (EPAct 92) mandates that all showerheads manufactured, sold, and/or installed in the U.S. operate at a flow rate that does not exceed 2.5 gpm (9.5 Lpm). Showerheads sold prior to 1994 will usually have higher flow rates; many of these showerheads still exist in homes and apartments.
For example, prior to 1980, many showerheads exceeded 5 gpm (18.9 Lpm) in flow rate. In the mid-1980s, a number of states restricted flows to 3.5 gpm (13.2 Lpm) maximum, and later reduced that even further to 3.0 gpm (11.4 Lpm). To eliminate confusion and eliminate the state-by-state differences in maximum flow rates across the U.S., EPAct 92 set the nationwide maximum flow at 2.5 gpm (9.5 Lpm), preempting state regulations. (NOTE: ON DECEMBER 22, 2010, the U.S. Department of Energy announced that Federal pre-emption of the states as to showerheads and other plumbing products has been waived. This means that states and local jurisdictions in the U.S. are now free to set their own showerhead performance requirements.)
Obviously, the duration of the shower also affects water usage. Initially, some water efficiency practitioners believed that reducing flow rates of showerheads would cause users to take much longer showers. That is, a person accustomed to a 5 minute shower at 5 gpm (18.9 Lpm) will take a 10 minute shower at 2.5 gpm (9.5 Lpm). However, studies performed in hundreds of homes across North America indicate that this is NOT occurring. Reductions in flow rates have only a minor influence on the duration of the average shower experience.
Shower flow restrictors are simple, inexpensive devices designed to lower the flow rate of the showerhead and reduce total water consumption. Restrictors can either be an integral (but removable) part of a new showerhead or they can be after-market inserts that are installed at a point between the shower arm and the showerhead itself.
Integral restrictors are used by the showerhead manufacturer to reduce the flow and meet a prescribed flow rate (EPAct 92, WaterSense, or some other efficient flow rate). In many cases, restrictors can be removed easily, usually for cleaning. But, by providing for removal, they enable the user to readily increase the flow rate to a level that exceeds the prescribed maximum. Some manufacturers choose to circumvent Federal, State or Provincial maximums by including information in or on their packaging showing the user exactly how to remove the restrictor and achieve a non-compliant flow rate.
In the after-market, flow restrictors are readily available at hardware, home improvement, and big box stores that can be used to reduce the showerhead flow rate to some more-efficient rate. In some past instances, however, the restrictor rendered the shower experience unsatisfactory (lower pressure and force) to the user. The recent introduction into the marketplace of high-efficiency showerheads (2.0 gpm (7.6 Lpm) and lower) has led water and energy utilities to substitute complete showerheads for flow restrictors in their free distribution programs. These new showerhead products are priced competitively and meet the strict performance and flow rate requirements of the WaterSense program.
Simple shower timers for use in the home are available in a variety of designs, including both hourglass sand-timer types as well as battery-operated digital models. While these products usually don't sound an alarm and don't close the shower valve when they reach their timer's limit, they do provide information to the water-conscious user in the shower. Furthermore, they are provided by water utilities to their customers as an effective outreach tool and a novel, but helpful, aid to the customer.
Traditional spring activated kitchen timers (with an alarm bell or chime) can be used for the same purpose in the shower.
An additional, but potentially more dangerous, method to reduce water use in showers is to (a) use a showerhead with a "trickle" valve OR (b) turn off the water fully while lathering and shampooing. The method generally involves the user....
1) turning on the water to rinse the body and hair;
2) turning off the water while shampooing hair and washing body, either using a showerhead with an independent shut-off and "trickle" feature or closing the valve(s) at the main water supply to the shower; and
3) resuming water flow and rinse off all shampoo and soap.
Using this technique, the duration of water flow can be reduced to 2 minutes or less by the highly motivated user. This is most easily performed when an on-off "trickle valve" is integral to the showerhead. When such is not the case, separate shut-off or "trickle valves" can be purchased at many hardware and home improvement stores, and are installed between the shower neck and the showerhead.
However, while such a mid-showering shut-off approach has the potential to save water, not all homes and apartments can (or should) use these devices. In cases where a pre-1987 (approximate) two-handle shower valve system (without an automatic compensating valve behind the wall) is installed, the risk of scalding and thermal shock exists.
For example, in households where the water pressure on the cold water side differs from that on the hot water side, temporarily closing the valve at the showerhead (step 2 above) could result in hot water flowing into the cold water leg or vice-versa. Depending upon the length of time the valve is closed and the difference in line pressures, the temperature of at the exit point of the showerhead can be significantly different than it was prior to closure. When the valve is re-opened, the water is at a higher or lower temperature than when it was shut and, as a result, a shock to the body can result, potentially causing a slip and fall. In addition, where hot water has backed up into the cold water line, scalding can result.
For these reasons, showerheads with integral shut-off valves or separate valves designed to be installed between the shower arm and the showerhead are not recommended in the following cases: (1) pre-1987 homes where no scald protection valve is installed behind the wall; (2) showers with flow rates below 2.0 gpm (7.6 Lpm); and (3) showers that are used by elderly or infirm people more easily subject to thermal shock, slipping and falling.
For more information on the hazards associated with scalding and thermal shock in the shower, read this white paper by the American Society of Sanitary Engineers.
Read this warning statement now being attached to plumbing and green building codes and standards in North America.
Read this article in Home Energy Magazine regarding the topic of scalding and thermal shock.
Read this very descriptive article on automatic compensating valves in Plumbing Engineer magazine.
With rare exception, recirculating showers are not designed or operate in a water-efficient manner. These systems are often called "vertical body spas" and they almost always use more water than a typical shower or bath. The re-circulation pumps require a reservoir of water in the shower basin to operate properly. Some makes and models of these systems require more than 45 gallons (170 L) of water in a basin, tub, or other sump - as much as 10 times the water usage of an efficient shower in the hands of a water-conscious user. Not only that, the user usually cannot use any soap or shampoo during the system operation, because the recirculating system could be rendered ineffective and the spray heads will emit these suds at a very high velocity. In most cases, the user must take a "real" shower after the recirculating shower, adding additional water usage to the event. Recirculating showers are NOT recommended in residential applications.
Two trends are troubling to water efficiency advocates in North America:
Multiple Showerhead Systems in a Single Stall
There is a growing trend to install multiple showerhead systems in single user shower stalls (compartments) in homes. While not illegal, such systems subvert the intent of the Federal maximum of 2.5 GPM (9.5 LPM) flow rate for showerheads as contained within EPAct 92.
Fortunately, nearly all of the North American green codes and standards are addressing the multiple showerhead issue by defining the size of a showering stall and next specifying the maximum cumulative flow of all the showers and other water emitters within the stall.
Besides multiple showerhead systems, another area of recent and significant concern by water efficiency advocates is the sale of EPAct-non-compliant showerheads over the internet and in U.S.-located kitchen and bath showrooms. Numerous blatant violations of EPAct 92 were disclosed to the U.S. Department of Energy (DOE) by water providers and the Plumbing Manufacturers Institute (PMI) in December 2005. Non-compliant showerheads (with advertised and actual flow rates of 10 gpm (38 Lpm) and greater) and test reports from an accredited laboratory were furnished to the DOE by the PMI in accordance with the DOE process. Unfortunately, the DOE failed to act upon these violations until 2010. As a result, non-compliant showerheads entered the chain of commerce and were sold to consumers for 4 additional years without any action by the authorities.
In 2010, the DOE belatedly began enforcement actions against a number of manufacturers in non-compliance with the law.
Peter Gleick, President of the Pacific Institute, summarized his opinions on the "Water Scofflaws" (manufacturers offering non-compliant products) and the DOE actions in 2010.
North America is faced with a trend of ever-increasing shower flow rates and water use within new homes as a consequence of these trends. While such concerns were originally confined to what some may classify as the new and remodeled "luxury" home, it is evident that the trend is making its way into other homes as well. This includes multiple showerheads in a single system, "rain" type shower systems with excessive flow rates, and shower "spas". The extent to which that is happening is not clearly defined, but some generalized descriptions of the trend may be found in the following sections.
This short document provides selected quotations from various interior design trade publications on the topic of the "shower experience". The reader must recognize that these trade publications and their articles are directed at the market for major remodeling and new construction projects. The terms used by the authors of the various statements may, to some extent, exaggerate the significance of these trends.
Sponsored by Seattle Public Utilities, LBNL undertook to assess the impact upon residential water use of non-compliant and multiple-head shower systems. This study was a broad overview of the possible market penetration of such systems, the likely water consumption, and measures that might be taken to reduce water use in residential showers.
Biermayer, P. (2006) Potential Water and Energy Savings from Showerheads
Biermayer, P. (2005) Showerheads - Current Market Trends and Potential Loss of Savings
This presentation, titled "Trends in Shower Design and Their Effect on Energy and Water Use", was given at the ACEEE Summer Study in August 2006. It reflects the findings of the showerhead study listed above as well as additional information on energy and water use.