Water Efficient Toilets

Water saving toilets use less water (or potable water) than average to convey sewage.
photo credit: Charles & Hudson at Greenbuild via Flickr

Average Gallons Per Flush

In the United States, federal law requires that toilets can only use a maximum of 1.6 gallons per flush (gpf). While most toilets on the market are 1.6 gpf because of this standard, there are many options on the market that use much less. In fact, some dry toilets use as low as 0.2 gpf. This is much better than older toilets from the 1990s, which use as much as 5 gpf.

Since 1.6 gpf is the market standard in the U.S., a water efficient toilet uses fewer than this to flush. The following toilet models and their average gpf can help you to decide which type of water saving toilet to choose.

Types of Toilets and Average Water Use

• Gravity Fed (1.6 gpf, 1.28 gpf)
Gravity fed toilets are what you would consider a conventional, average toilet. They have a tank, which holds water, which pours via gravity into the bowl when flushed. The water refills after flushing, and stops when it reaches a certain height in the tank.

• Pressure-Assist (1.6 gpf, 1.1 gpf)
A pressure assist toilet also has a tank, but the tank contains pressurized air inside a vessel. The flush releases the pressurized air, which helps the water to flush.

• Dual Flush (1.6 gpf, 1.0 gpf)
A dual flush toilet is a type of gravity-fed toilet that has two buttons: one for a small flush (liquid waste) and one for a large flush (solid waste). A dual flush toilet that uses 1 gpf for liquids and 1.6 gpf for solids averages 1.28 gpf or less.

• High-Efficiency Toilet (HET)
High efficiency toilets use 20% less water than the 1.6 gpf standard. Some use even less, at 1.1 gpf.

WaterSense is the Environmental Protection Agency’s label for water saving fixtures and appliances. It labels HETs that use 20% less water and meet high standards for performance, warranty and efficiency. These toilets can save up to 4,000 gallons of water per year, which amounts to over $90 on water bills.

• Composting Toilet (0 gpf)
A composting toilet uses little or no water for sewage conveyance, because the waste is eliminated via the natural processes of decomposition. The waste can go directly into the ground, or it can be stored in a tank for composting later.

Free LEED GA Practice ExamDual Flush Toilets on the Market

As previously mentioned, dual flush toilets save water by giving the user the ability to use less water to flush liquid waste and more water for solid waste. Many dual flush toilets use 1.6 gpf or less for the solid flush, meaning it uses less water than a conventional toilet. For example, a dual flush toilet that uses 1.1 gpf for liquids and 1.6 gpf averages 1.28 gpf or less.

The following are two dual flush toilets and one dual flush converter that are currently on the market.

1. Caroma Dual Flush Toilets

The Australia-based Caroma offers a big line of water efficient bathroom technologies for many types of residential and commercial purposes. They are a huge leader in water efficiency, with the highest number of WaterSense labels for their toilets.

The company offers dual flush toilets with 1.6 gpf for solid flushes and 0.8 gpf for liquid flushes, or 1.28 gpf for solids and 0.8 gpf for liquids.

One of Caroma’s innovative toilets is the 305 Round Front Plus, which combines a toilet and sink. The user washes their hands in the sink, and that water than travels into the tank, where it is reused for the flush.

2. TOTO Aquia Dual Flush Toilet

TOTO’s Aquia dual flush toilet which sells for between $385 and $1,000 (depending on the model), uses 1.6 gpf for solid flushes and 0.9 gpf for liquid flushes. It is high quality, coming from the world’s largest plumbing manufacturer. The EPA has named TOTO as the only plumbing manufacturer to be a Water Efficiency Leader, which is awarded for its efforts to make water saving products.

3. MJSI Hydroright Dual Flush Converter

MJSI’s Hydroright Dual Converter is a technology for retrofitting existing toilets. When installed, which takes 5-10 minutes without tools, it can save up to 30% of the toilet’s water use. It’s inexpensive, at only $20.59 on Amazon, and has won awards from Sustainable Industries and Home Depot for it’s ingenuity and quality.

Composting Toilets

The following 3 composting toilets are currently on the market, and can be used for green and LEED certified building projects.

1. Ecovita Separett Villa

Ecovita's Separett Villa, which sells for $1,249 on the company’s website, is designed to feel like a conventional, modern water flush toilet. It is made from recyclable high-gloss polyethylene and uses a urine diverter, which prevents the mixing of solids and liquids and prevents odor. It has a view guard for solid waste (which slides back when the user sits). The solid waste is collected in a container, which can be replaced with a new container when full. It uses no water, but does use electricity or a battery to power a small fan.

In 2009, Sustainable Industries Magazine selected it as one of the top 10 green building products.

2. Envirolet FlushSmart Vacuum Flush

The FlushSmart VF from Envirolet can flush waste up to 70 feet away by using a small amount of water (as little as 0.2 liters per flush). This makes it first combined vacuum flush and composting toilet, which makes it easier to install in places like basements and cottages on rock, and eliminates the need for gravity.

The Envirolet is easily installed with its "plug and play" technology.

The FlushSmart ranges from $3,199.20 to $5,423.20 on Envirolet's website, depending on the specific model.

3. Sun-Mar Excel

The Australian toilet manufacturer, Sun-Mar, offers the Excel, one of it’s many types of composting toilets, and the first composting toilet to be certified by the National Sanitation Foundation. The toilet, which is the best selling composting toilet in North America, has an electric flush and can be used in homes and in light commercial applications. It costs $1795.

Sun-Mar also offers the Excel-NE, which has a non-electric flush.

Toilet Retrofit

Many old toilets use much more water than the standard (1.6 gpf). Instead of buying a new toilet, you can use inexpensive or homemade solutions to make your existing toilet more water efficient.

For example, you can fill plastic water bottles with something to weigh it down, like sand or pebbles, and screw on the caps. Then, place them in the tank, a safe distance from the plumbing system.
Alternatively, you can purchase a cheap tool to reduce your toilet’s water use. For example, you can buy a float booster for about four dollars, or a tank bank, for about $1.75 at Eartheasy.

Or, as mentioned previously, if you'd prefer a more sophisticated, tried and true system for reducing your toilet's water use, check out a dual flush converter, such as MJSI's Hydroright. The Hydroright dual flush converter, which can be installed in 5-10 minutes without tools, is shown to reduce water usage by 30%.

Water Efficient Toilets and LEED

According to the New Construction 2009 rating system, water efficient toilets could contribute to the following credits:

• WE Prerequisite 1, Water Use Reduction (0 points):
This requires a 20% reduction in baseline water usage.

• WE Credit 2, Innovative Wastewater Technologies (2 points):
This credit aims to reduce demand for potable water by reducing potable water use for sewage by 50% or treating 50% of wastewater to tertiary standards. Water saving toilets can help with the first option by reducing the amount of potable water used for sewage.

• WE Credit 3, Water Use Reduction (2-4 points):
This credit is the same as WE prerequisite 1, except with greater percentages of water reduction. LEED projects can earn 2 points for 30% water use reduction, 3 points for 35% reduction, and 4 points for 40% reduction.

Additionally, water saving toilets could contribute to the LEED for Existing Buildings: Operations and Management (EB:O+M) rating system under Water Efficiency (WE) Prerequisite 1, Minimum Indoor Plumbing Fixture and Fitting Efficiency (0 points).


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