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Demand Pumping System

Building Science-to-Sales Translator

Demand Pumping System

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Technical Description

Traditional hot water distribution systems consist of a trunk and branch layout. This consists of a relatively long, large-diameter main line that feeds smaller branches that flow to plumbing fixtures or split to serve multiple fixtures. Even in relatively small homes of 1,200 square feet, the volume to the furthest fixture can exceed 1.5 gallons and the time to the tap can be more than 90 seconds. An effective option for saving water in new homes is to lay out the plumbing in "series" to each fixture and appliance with a dedicated return to the water heater from the most remote location (This is called "structured plumbing"). An in-line pump is installed near the water heater to move the cold water sitting in the pipes back through the water heater before it comes out of the hot water tap, to reduce the amount of water wasted while waiting for hot water. A similar system can be set up for existing homes that locates the pump at the most remote fixture. To save energy, the pump can be set up as an "on-demand" system that is activated by a sensor or switch to avoid the needless calculation of hot water that occurs with inefficient, continuously recirculating pump systems. DOE’s Zero Energy Ready Home program requires that no more than 0.6 gallons of hot water be discharged from a hot water fixture before hot water delivery. Recirculation pump systems must be based on an occupant-controlled switch or an occupancy sensor.

Alternate Terms

Water and Energy Saving Hot Water Distribution
On-Demand Hot Water Circulation Technology

Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.