Toilets

Get Rebates,
Incentives & Services

Introduction

The United States uses about 5.8 billion gallons of water every day to flush waste. Since toilets and urinals account for nearly one-third of building water consumption, there is a significant potential for savings. Ultra-low-flush (ULF) toilets use no more than 1.6 gallons per flush (gpf) rather than 3.5 to 7 gallons of water used by other designs.

Technology Options

Current Federal law requires that residential toilets manufactured after Jan. 1, 1994, must use no more than 1.6 gallons per flush (gpf). Commercial toilets manufactured after Jan. 1, 1997, must use no more than 1.6 gpf; urinals must use no more than 1 gpf. ULF toilets are required in all new construction in California as of January 1, 1992. This statewide requirement was passed to promote water conservation.

ULF toilets use an efficient bowl design and increased flushing velocities to remove waste, rather than simply using a large amount of water for flushing. There are two main varieties of low-flush toilets: gravity flow and pressurized tank systems. The gravity flow technology is also used for conventional toilets. When flushing an ULF toilet, however, the rim wash can come through an open slot rather than through little holes. The bowl may have steep sides and a narrower trapway. These changes to the design of the toilet bowl cause a quick release of water, creating a siphon action to pull the waste out. The pressurized flush is a new design developed for 1.6 gpf residential toilets. It uses the house water line pressure to increase the velocity of the water going into the bowl. Within the toilet tank incoming water presses against a rubber diaphragm that compresses a pocket of air. The water is released by pushing the flush valve.

For institutions like prisons or hospitals, non-ceramic, metal toilets are available. They have straight drain lines and a flush rate of 0.5 gallons per flush (gpf). Replacing 3.5 gpf with 0.5 gpf toilets can lead to lifetime water savings even larger than those shown below in the Benefits section.

Installation and User Tips for Commercial Facilities

    For initial installation of a low-flush toilet, "snake" drain lines and replace the entire fixture. After a low-flush gravity tank unit is in operation, only the valve and ballcock need be replaced if the rest of the fixture still functions.

    With flush-valve toilets, make sure valves are properly adjusted. Leaky valves are a source of enormous water loss in both flush-valve and tank toilets, and are especially common in hard-water areas. These leaks are often invisible and inaudible. Semi-annual dye tablet testing is a simple and inexpensive way to detect leaks.

Efficiency Benefits

By using a ULF toilet instead of a standard 5-gpf toilet, a household of four people could save approximately 60 gallons per day, or about 22,000 gallons per year.

A commercial facility that replaces a typical existing 3.5-gpf toilet with a standard new 1.6-gpf unit could cut its annual water use by more than half and save hundreds of dollars in water costs, assuming 30 flushes per day for 260 days (see chart below). (Savings vary with water cost, flow rates, electricity or gas costs and expected usage.)

Cost-Effectiveness Example
Performance Typical Existing Unit New Standard Unit Best Available Unit
Gallons per flush (gpf) 3.5 gpf 1.6 gpf 1.0 gpf
Annual Water Use 27,300 12,500 7,800
Annual Water Cost $110 $50 $30
Lifetime Water Cost $880 $400 $250
Lifetime Water Cost Savings (for replacing existing unit 10 years early) - $480 $630
Metric Conversion: 1 gallon = 3.8 liters Cost Effectiveness Assumptions: Savings estimates are based on an existing flush rate of 3.5 gpf. Usage assumption: 30 flushes per day, and 260 days per year. Assumed combined water and wastewater price: $4.00/1000 gallons.
Source: DOE, FEMP, FYP

Manufacturers

Toto, Niagara, and Mansfield are some top-rated manufacturers of high-efficiency toilets. Additionally, the NAHB Research Center (NAHBRC), in cooperation with Seattle Public Utilities in Washington, and the East Bay Municipal Utility District in Oakland, Calif., has released a water closet fixture performance study (PDF, 16K) that took place in 2002. The report details the results of extensive performance testing on 49 of the most popular ultra-low-flush (ULF) toilets in the United States.

California Urban Water Conservation Council (CUWCC) compiled a side-by-side comparison of Consumer Reports and the NAHBRC's performance ranking of all ULF toilet models. CUWCC also offers a full report on the Maximum Performance testing of over 840 toilet models.

Purchasing Tips

Ultra-low-flow toilets come in a range of prices. Many models are available for about $100 and can run as high as $400 or more for the decorator models. ULF toilets can be purchased in the same spectrum of decorator colors as conventional toilets. Various styles are available in plain rim, elongated rim and high handicapped models. ULF toilets install just like conventional toilets, making them ideal for remodeling and new construction. No special hook-ups or tools are needed.

  • When buying from a commercial source (retailer or distributor), select or specify models with flush rates that meet the recommended level. Start with this list of water-efficient toilet units, rated one to five by Consumer Reports.
  • Evaluate new performance standards and testing criteria released by the American National Standards Institute (ANSI) in December 1990. All ULF toilets have to meet these standards to be listed by the International Association of Plumbing and Mechanical Officials (IAPMO).

Emerging Technology

A proposal to amend the current national standard for dual-flush toilet fixtures is currently being considered by the Standards Committee. The water industry supports this proposal. The primary purpose of the dual-flush water closet is to achieve water conservation benefits over and above those yielded by the conventional 1.6-gallons per flush water closet. This is accomplished by providing the user with a reduced flush mode for liquid- (urine) only flushes.

Dual-flush water closets are currently being sold in the United States and Canada by two manufacturers, Kohler and Caroma U.S.A. Wash-down bowls are non-siphonic and use the weight and volume of water to "push" the waste from the bowl, while siphonic bowls are designed to "pull" the waste from the bowl. The wash-down design is typical of dual-flush water closets sold elsewhere in the world with a reduced flush volume of approximately 0.8 gallons (3 liters). A number of these wash-down type closets have been installed in the United States and Canada.