Water Use and Collection

BIM for Architecture, Engineering, and Construction Curriculum


Improving Plumbing Fixture Efficiency

What are the advantages and disadvantages of using high-efficiency plumbing fixtures? Are they more costly to purchase? To install?

High-efficiency plumbing fixtures typically bring a sizable reduction in water use at a small cost. The initial cost to purchase these fixtures is often slightly higher than standard fixtures, but this one-time cost is quickly offset by the continuous water savings for years to come.

High-efficiency plumbing fixtures are usually no more expensive to install than standard fixtures. The differences are typically limited to the flush valve mechanism. No additional piping or preparation is needed.

What high-performance fixture options are available for:

 - Toilets?

Several types of high-efficiency toilets are available. Low-flow toilets that consume less water with each flush have been available for many years. Dual-flush toilets (which offer two flushing modes\u2014less water for liquid waste and more water for solid waste) have been used around the world for many years and are now being introduced in the United States.

- Urinals?

Urinals with low-flow valves are typically installed in most new public restrooms to conserve water. Waterless urinals have been introduced and are becoming more common, but are not yet widely used. 

- Showers?

Low-flow shower heads offer a quick-and-easy strategy for dramatically reducing the water consumed during a typical shower session. Low-flow mixing valves and timers are also available, but they are much less common. 

A related issue that affects water consumption is how the water is heated. When water is heated at a central tank and piped to a remote shower, much water is consumed as people run the shower to clear the cold water in the pipes and wait for the hot water to be delivered. Tankless water heater systems help to reduce this water waste by instantly heating the water near the shower on demand. 

Recirculating hot water systems can also help reduce water waste by pumping hot water through the pipes, so hot water is always nearby. Of course, the energy cost of continually heating the water and pumping it through the pipes should also be factored when considering this strategy.

- Lavatory Sinks?

Low-flow faucet heads are available but not commonly used. More attention is usually focused on the faucet controls to limit the duration that the water is running.

How can automatic sensors (for example, on lavatory sink faucets) be used to reduce water use?

Automatic sensors can dramatically reduce the water used at a lavatory sink by stopping the water flow when nothing is using it. When hands are detected by the sensor, water flows; when hands are no longer detected, water stops. Sensors are commonly used in new public restrooms but are far less common in residential settings.

Another low-tech approach with a similar effect is spring-loaded faucet valves that cut off the water after a fixed time period has elapsed.

Net-Zero Measures

What types of plumbing fixtures produce greywater?

Greywater that can be reused is typically produced by lavatory sinks, showers, washing machines, and other devices that drain water that does not contain any sanitary waste.

What applications can greywater be used for?

Greywater is often used for flushing toilets and urinals and landscape irrigation.

What changes are required to plumbing systems to collect and use greywater?

To implement are greywater system, a secondary set of drain pipes must be used to divert water from greywater-producing fixtures into a collection system (rather than into the sewer system). A secondary set of water supply pipes must also be provided to transfer the greywater to the fixtures and devices that will use it.

What other net-zero sources of water (besides rainwater collection) can be used in climates where rainwater is not plentiful?

Where rainwater is not plentiful, groundwater collection systems of wells and pumps offer another net-zero source of water.

If the roof surface available is not sufficient to meet the rainwater harvesting area required, what other strategies can be used for collecting rainwater?

Rainwater can also be collected from ground surfaces and landscaping. For example, the runoff from a paved parking lot or landscaped area can easily be diverted to a cistern (rather than flowing into the storm sewer system). Rainwater collection systems can also be installed under grassy playing fields, which typically provide a large, relatively unobstructed collection area.