Code Changes and Implications of Residential Low Flow Hot Water Fixtures

Practical solutions to improve hot water distribution systems and overcome market adoption barriers.

Building Decarbonization

Gary Klein and Associates, Inc.

Recipient

Rancho Cordova, CA

Recipient Location

8th

Senate District

8th

Assembly District

beenhere

$249,900

Amount Spent

closed

Completed

Project Status

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Project Result

The project provided strategies to improve hot water distribution in single-family homes to achieve reductions of distribution and waste water & hot water delivery quality improvement. These strategies include improvements to distribution systems, pipe layout optimization, use of two water heaters, moving water heater closer to the fixtures, pipe size reduction, compact architectural design, and lower-flow fixtures. Test results show a distribution performance model, simulating transient hot water delivery operation in complicated distribution networks. Performance assessment results, estimates of improved distribution designs and distribution losses can be reduced by more than 50% with system energy water consumption by more than 25%.

The Issue

Appliance standards have been steadily reducing the maximum allowed flow rates for hot water fixtures. However, with little change in distribution system designs, building occupants using low flow fixtures will experience longer waiting time for hot water and lower delivered hot water temperature. There has not been any study that systematically addresses these issues and the impact of low flow fixtures on hot water system performance. Without carefully addressing these issues, low flow fixtures may not be able to achieve the intended energy and water savings, and market adoption of low flow fixtures could be hampered.

Project Innovation

This research analyzes and recommends future code changes to hot water distribution systems for improvements to piping design in new construction and existing buildings. The research provides solutions to overcome market adoption barriers, identifies distribution improvement strategies, and demonstrates how to apply the identified strategies to a range of building designs.

Project Benefits

The project resulted in recommendations for code changes to improve hot water distribution systems. If new homes were built incorporating the results several benefits would accrue to the State. First-year savings from one home with distribution improvements would be 11- 19 therms, 1750-3180 gallons of water; and $1500 to the builder. The higher savings includes distribution improvements with lower-flow fixtures. On average about 100,000 new single-family homes are built in California annually. Cumulative savings in ten years from distribution improvements would be 59-107 million therms and 9.6 to 17.5 billion gallons of water. this translates to about 310,000-565,000 metric tons of CO2e reduced.

Affordability

Following adoption of distribution improvement code changes developed by this project, new Title 24 compliant homes would on save 11-19 therms of natural gas and 1750-3180 gallons of water annually along with reductions in building cost to the builder due to compact designs. Assuming average cost of residential natural gas of $1.50/therm and $1.50 per 100 cubic feet of water, annual cost savings per home will be approximately $367 to $666.