Universal Design Consortium Inc. © 2010 All rights reserved | Privacy Policy | Terms of Use

It's not just low flow, it's the law. In 1995, the National Energy Policy Act mandated the use of toilets that use no more than 1.6 gallons of water per flush. Since then, low-flow plumbing fixtures including toilets, faucet aerators and showerheads have been developed that save substantial amounts of water compared to conventional fixtures while providing the same utility.

Different types of low-flow toilets use various technologies aimed at making the toilet more functional. Some toilets have large drain passages, redesigned bowls and tanks for easier wash down. Others supplement the gravity system with water supply line pressure, compressed air, or a vacuum pump.

Conventional faucet aerators don't compensate for changes in inlet pressure, so the greater the water pressure, the more water you use. New technology compensates for pressure and provides the same flow regardless of pressure. Aerators are also available that allow water to be turned off at the aerator itself. Showerheads use similar aerator technology and multiple flow settings to save water.

Low-flow toilets use a maximum of 1.6 gallons of water per flush compared with about 3.5 gallons of water used by a standard toilet. Low-flow shower heads use about 2½ gallons of water per minute compared to between four and five gallons per minute used by conventional heads. Low-flow faucet aerators can cut the water usage of faucets by as much as 40% from 4 gallons per minute to 2½.

Toilets

Designed for water conservation, high efficiency toilets (HETs) have been defined by the plumbing industry and the Environmental Protection Agency (EPA) as those that use an average of 20 percent less water per flush than the industry standard of 1.6 gallons (or, 1.28 gallons). Using a high efficiency unit (in place of 1.6 gallon flush units) can save up to 8,760 gallons of water each year for a family of four with average daily flushes of six each. In municipalities like Washington, D.C. this roughly translates to a water/sewer usage annual savings of $50. Savings will be greater in climates were water is in shorter supply.

Gravity Fed Single Flush Toilets
Gravity fed single flush toilets operate the same way as any standard toilet, however, they use less total capacity per flush. Typical flush capacities that are available for these models are 1.1 and 1.28 gallons.

Dual-Flush Toilets
Designed for light and heavy flushes, dual-flush toilets tend to average less than 1.2 gallons per flush. They meet HET criteria of 1.28 gallons per flush or less (HET criteria for dual flush toilets identifies the effective flush volume as the average of one high flush and two low flushes). Dual flush models are available from many well-known manufacturers with light flush capacities from .8 to 1.1 gallons and heavy flush capacities from 1.3 to 1.6 gallons per flush. These toilets typically operate with a handle that can move up or down, or a two button system. One direction or button will activate the lower flow flush, while the other will activate the higher flow flush.

Pressure Assist Toilets
Pressure assist, or pressurized tank, toilets are another high performance, low consumption alternative. These toilets use either water line pressure or a device in the tank to create additional force from air pressure to flush the toilet. The device in the tank could either be a storage device with compressed air that would require replacement or a tank that creates pressure when the tank is being filled. These toilets typically average 1.1 to 1.2 gallons per flush. Some pressure assist systems move a greater volume of water at a significantly lesser volume of sound.

Power Assist Toilets
Power assist toilets operate using a pump to force water down at a higher velocity than gravity toilets. Power assist toilets require a 120V power source to operate the small fractional horsepower pump. Typical flush volumes are between 1 and 1.3 gallons per flush and dual-flush models are also available.

Plumbing Manifold

A new method for residential water distribution is gaining acceptance in the home building industry. Manifold plumbing systems are control centers for hot and cold water that feed flexible PEX supply lines to individual fixtures. Manifolds together with plastic piping offer installation-related cost advantages over conventional rigid pipe plumbing systems.

Separated manifold chambers or separate manifolds can serve hot and cold water lines. The cold water manifold is fed from the main water supply line and the hot water manifold is fed from the water heater. Water pressure in manifolds is maintained by the incoming service line. A water line dedicated to each fixture eminates from a port in the manifold. Manifolds can be centrally located at the water service line entry point, or in larger homes or aparment buildings, mini-manifolds can service remote fixture groups.

Manifold systems can accept all common supply line sizes, down to 3/8-inch. Typically, a parallel supply line layout or a hybrid version of this will be used with a manifold, so fewer fittings are required (hence, less pressure drop occurs in the lines.

Fixtures

The use of water-saving devices has increased dramatically since the 1992 Energy Policy Act mandated the use of low-flow plumbing fixtures. However, the trend has not gone undetected. Some people don't like the feel of aerated water or complain that it splashes too much. A new product is available that makes a low water flow feel more like higher flow. In the last few years, laminar flow fixtures have become more popular in residential applications. Plumbing manufacturers have started to equip faucets with laminar devices to create a distinctive look.

Controls for laminar flow fixtures deliver a precise volume of water at faucets, showerheads, and hose outlets, typically 1.5 to 2.2 gallons per minute (gpm). Fixtures equipped with laminar flow controls deliver a constant rate, unlike conventional water-saving fixtures that deliver varying flow rates in response to varying line pressure,. According to the manufacturer, the laminar flow pattern gives the feeling that water is flowing at a higher rate than it actually is. Under the same flow rate/pressure conditions, aerated streams actually tend to feel “lighter” because they mix air and water, laminar streams are heavier (water only) and feel stronger.

Laminar flow controls work differently than faucet aerators. Aerators add air to the water stream to make the flow feel stronger. Laminar flow controls, on the other hand, work by producing dozens of parallel streams of water. When the faucet is open, water flows in a clear, solid-looking stream, and does not splash. Objects are wetted quickly and evenly with less mess, according to the manufacturer.

Air induction system

Low water consumption faucets allow for greater water conservation.

Low water consumption shower heads allow for greater water conservation.

Water manifold controls more than one watering zone within the building.

Flex water lines installed into a building.