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Best Management Practice #6: Toilets and Urinals

Toilets and urinals can account for nearly one-third of a building’s water consumption. Inefficient or poorly maintained toilet and urinal fixtures can be a major source of water waste in commercial, residential, and institutional buildings; thus, significant savings are possible in this area.

Overview

Several types of toilets and urinals are available for residential, commercial, and industrial use. Builders, plumbers, and federal agencies need to ensure that fixtures are water efficient and that they choose the most appropriate fixture for specific applications. 

Toilets

Two common product categories of toilets are tank, which are typically found in residential buildings and flushometer, which are common in commercial buildings.

  • Tank Toilets: Two common types of tank toilets are:
     
    • Gravity-style. This type of toilet sends water from the tank into the bowl by releasing a flapper valve between the tank and the bowl.
       
    • Pressure-assisted. This type of toilet has a vessel inside the tank with pressurized air. When the toilet is flushed, the pressurized air pushes the water into the bowl at a high velocity to create a powerful flush.
       
  • Flushometer Toilets: Flushometer toilets send pressurized water directly from the supply line through a flush valve and into the bowl to create the flush. 
Urinals

The two main types of urinals are flushometer and nonwater. 

  • Flushometer Urinals: Flushometer urinals send pressurized water directly from the supply line through a flush valve and into the urinal fixture to create the flush. 
     
  • Nonwater Urinals: A nonwater urinal does not flush water but has a cartridge in the bottom that contains a sealant whereby waste flows through the cartridge and into the drain line.
Flushometer Flush Valves

Two common types of flush valves for flushometer toilets and urinals are diaphragm and piston valves. For details, see Diaphragm and Piston Valves below.

Sensors

Flushometer toilets and urinals can be equipped with electronic sensors that automatically flush the fixture. Automatic flushing toilets and urinals do not save water; rather, they are intended to provide health and sanitary benefits because the user does not have to touch the flushing mechanism.

Federal law requires tank and flushometer toilets to use no more than 1.6 gallons per flush (gpf) and urinals to use no more than 1.0 gpf. High-efficiency toilets (HETs) and high-efficiency urinals (HEUs) are more efficient than federal efficiency standards. HETs consume no more than 1.28 gpf; HEUs consume no more than 0.5 gpf. The U.S. Environmental Protection Agency WaterSense Program released specifications for tank-type HETs and flushing HEUs. Federal sites are required to purchase WaterSense-labeled toilets and urinals or equivalent. For more information, see Energy- and Water-Efficient Products.

Flushometer toilets and urinals contain a flush valve.  Two common types of flush valves are diaphragm and piston valves. 

Diaphragms and Piston Valves

Flushometer toilets and urinals contain a flush valve. Two common types of flush valves are diaphragm and piston valves.

  • Diaphragm Valves: A diaphragm valve has a rubber disk or diaphragm that separates the upper and lower chambers in the valve housing. When the toilet is flushed, the relief valve is tilted. This creates a pressure imbalance in the valve that allows the diaphragm gasket to flex and thereby moves water at a consistent flow rate through the valve and into the bowl. Immediately after the flush, water fills the upper valve chamber through the diaphragm’s bypass orifice, which is a small hole in the gasket. As water enters the bypass orifice, the water pressure differential between the upper and lower chambers pushes the diaphragm back into place. This seals the valve and shuts off the water flow. A dirty or brittle gasket may not seal properly and should be replaced. If the water pressure is not sufficient, the diaphragm may not fully seal. This can cause the valve to remain open resulting in continuous water flow. 
     
  • Piston Valves: A piston valve has a plastic or brass contoured cup bordered with a narrow rubber lip seal that separates the upper and lower chambers in the valve housing. When the toilet is flushed, the relief valve is tilted. This creates a lower pressure in the upper chamber, which causes the contoured cup (acting as a piston) to rise and allows water to flow quickly from the inlet pipe, under the piston, and into the bowl. Immediately after the flush, a small water stream flows through a bypass orifice in the piston to restore water and pressure to the upper valve chamber. This return of pressure subsequently pushes the piston assembly down to shut off the water flow. A piston valve may contain a debris screen that may help to limit clogging in the bypass orifice. However, the piston can leak water through the relief valve and may not seal properly if the rubber seal is worn. The piston valve remains closed under conditions of low water pressure.
Operations and Maintenance

Federal agencies should develop a regular maintenance program to maintain water efficiency in toilets and urinals.

Tank Toilets
  • Ensure the water in the tank is set to the manufacturer’s recommended level and is not running over the overflow tube.
     
  • Adjust the float if water level is too high. 
     
  • Ensure that the fill valve (the mechanism that refills the tank after each flush) is working properly and not running constantly.
     
  • Periodically test the flapper valve for leakage and repair if necessary: 
    • Drop dye or food coloring into the tank water. 
       
    • Wait 10 minutes to see if the dye has seeped into the bowl through the flapper valve. 
       
    • If the dye has seeped, ensure that the flapper valve properly drops after a flush. 
       
    • Replace the flapper if the flapper valve is not fully dropping into place and seepage continues. 
       
    • Flush the toilet immediately after the test to avoid staining the bowl.
Flushometer Toilets and Urinals
  • At least annually, inspect the valves and check for worn parts. Long flush cycles or continuously running valves may indicate a clogged bypass orifice in the valve or improper sealing. The flush valve insert may need to be cleaned or replaced. (The flush cycle of a 1.6-gpf flushometer toilet or a 1.0-gpf urinal should not exceed 4 to 5 seconds.) A flushometer valves may include a debris screen, which can limit clogging of the bypass orifice. For further details, see Diaphragm and Piston Valves above.
     
  • When replacing a flush valve insert, make sure the flush rating of the replacement part matches the valve’s flush volume specification. For example, a 1.6-gpf flushometer toilet should only be retrofitted with a 1.6-gpf rated flush valve insert. This is particularly important for diaphragm valves because different rated diaphragms may be substituted in an existing valve that increases the flush volume. 
     
  • Ensure that the building’s water pressure meets the manufacturer-specified minimum pressure. Generally, diaphragm valves operate at 30 to 80 pounds per square inch; piston valves operate at 15 to 80 pounds per square inch.
     
  • Calibrate automatic sensors to ensure they are set properly to limit double or "phantom" flushing.
Nonwater Urinals
  • Clean and replace the sealant, cartridges, and material according to the manufacturer’s recommendations.
     
  • Educate users about the urinal’s water-saving benefits and ensure they are aware that water and other liquids should not be poured into the fixture because it can rinse out the sealant.
Outreach
  • Make sure maintenance staff are aware of each type of fixture’s maintenance and repair requirements.
     
  • Establish a user-friendly method to report leaks.
Retrofit

Toilets and urinals should not be retrofitted because retrofit devices can negatively affect their operation. Specifically, retrofits for tank-type toilets, such as displacement dams or bags, may hamper overall toilet operation and increase maintenance costs because they often have a short life span and require frequent replacement or adjustment. Early closure or valve inserts or replacement devices can reduce flush volumes by 0.6 to 2 gpf; however, they may require frequent replacement or adjustment,  may cause clogging and other flush performance problems, and may void warranties. Therefore, these retrofits are not appropriate for federal facilities. Other retrofit issues include:

  • For flushometer fixtures, do not retrofit only the toilet or urinal flush valves with high-efficiency valves. These retrofits will cause the fixture to flush improperly if the bowl is designed to handle more than 1.6 gpf for toilets or 1.0 gpf for urinals. Always replace the bowl and valve when retrofitting to high-efficiency fixtures.
     
  • Infrared or ultrasonic sensors that automatically flush flushometer valve toilets and urinals do not save water. Rather, these devices make toilet and urinal operation fully "hands free." 
     
  • Consider using alternative sources of non-potable water for toilet and urinal flushing (see BMP #14). Packaged gray water treatment systems provide water that is filtered and treated sufficiently for these uses. If you are using alternative non-potable water for toilet and urinal flushing, monitor the flapper valves and seals to determine any impact on their useful life.
Replacement Options

When considering the replacement of toilets and urinals, research and assess the site’s waste lines, water pressure, water quality, use patterns, and types of users (employees, residents, occasional members of the public, frequent visitors, etc.) to identify the appropriate fixtures.

The following replacement options help federal agencies maintain water efficiency across facilities.

  • Replace residential tank-type toilets with WaterSense-labeled products that have an effective volume of 1.28 gpf or lower.
     
  • Replace flushometer-type toilets with high-efficiency toilets that use no more than 1.28 gpf.
     
  • Replace urinals with WaterSense-labeled products or equivalent models that are designed to use 0.5 gpf or less. HEUs use as little as 0.125 gpf.
     
  • Ensure that the toilet and urinal valve and bowl have compatible flushing capacities.
     
  • When deciding between a diaphragm and piston flush valve type for flushometer toilets and urinals, consider valve design, restroom traffic, water quality, and operating system characteristics. For further details, see Diaphragm and Piston Valves and Operation and Maintenance above.
     
  • Check the performance of toilet models through the Maximum Performance Testing website, which provides performance results for numerous models of tank and flushometer toilets.
     
  • When possible, recycle used parts such as tank trim and metal flush valves (only the interior mechanism needs to be replaced) to minimize landfill impacts.