Drain-water heat-recovery system
From Swikipedia
Introduction
Drain water heat recovery system extracts heat from hot-water waste lines to preheat cold water before it reaches the water heater or tap. Thus, this is also known as gray water heat-recovery system and is especially useful when paired with on-demand or solar hot-water systems.
Brief Description
Hot water that goes down a drain carries away energy with it. This is 80–90% of the energy used to heat water in a home. Drain-water heat recovery (DHR) systems capture this energy to preheat cold water entering the water heater or going to other water fixtures
Drain-water heat exchangers can recover heat from the hot water used in showers, bathtubs, sinks, dishwashers, and clothes washers. They generally have the ability to store recovered heat for later use. A unit with storage capacity for use with a dishwasher or clothes washer is required. Without storage capacity, only useful energy during the simultaneous flow of cold water and heated drain water, like while showering will be available.
Heat exchangers for use in DHR vary in terms of pipe sizing, orientation of the drain line (horizontal, vertical, or other), and heat exchanger design. They also vary in cost and the amount of energy savings achieved.
Advantages:
Some of the advantages of drain water heat recovery system are:
1. They lead to high amounts of energy conservation
2. They are highly cost-effective
3. They have absolutely zero maintenance
4. They last longer
References:
http://www.greenbuildingadvisor.com/glossary
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13040
http://www.toolbase.org/Technology-Inventory/Plumbing/drainwater-heat-recovery
