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Solar Thermal Bypass Valve

Description

Install a code-compliant (UPC, IRC and IMC) valve assembly (solar bypass valve) on the cold water feed of the existing water heater to be used to connect the solar storage tank (see Figure 1). The solar bypass valve should be capped and labeled as an RERH component. Space requirements and layout for solar water heating and photovoltaic system components should be taken into account early in the design process. 

Solar bypass plumbing detail.
Figure 1. Solar bypass plumbing detail.

 

The EPA Renewable Energy Ready Home (RERH) Solar Water Heating checklist states:

“3.4. Install a solar bypass valve on the cold water feed of the water heater (cap and label both ends).”

Additional Notes:

Most solar water heating systems will require the installation of a separate hot water storage tank. The solar bypass valve makes future connections to this storage tank simple and affordable without having to drain the home’s existing plumbing system. The solar bypass valve should be installed on the cold-water feed of the existing water heater and should be configured in the following manner (see Figure 1):

  1. Install two “T” fittings in the “Cold Water Inlet” pipe that supplies cold water to the existing water heater.
  2. Install shut-off valves on each of the “T” fittings and one in the main pipe between the two “T” fittings.
  3. Stub-off and cap the two open-ended shut-off valves to prevent leakage should the valves be accidentally opened.
  4. Wrap a 3” x 1” label around each bypass valve so the text is visible and upright (if possible).  Each label should read, “Renewable Energy Ready Home Solar Thermal Bypass Valve.”

Builders should be aware that many municipal building codes now require that a backflow valve and pressure tank be installed on the cold water feed. A professional plumber should do this work.
Also worth considering, but not defined by this specification, is the installation of a floor drain. 

See the guides Utility Room Space, Mounting Surface for Pumps and Gauges, Solar Plumbing and Wiring Chase, and Architectural Drawing for more information about the Renewable Energy Ready Home (RERH) Solar Hot Water procedures.

Contributed by:

Pacific Northwest National Laboratory 

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References and Resources*

Solar Water Heating - Specification, Checklist and Guide

Publication Date
·
Author(s)
U.S. Environmental Protection Agency
·
Organization(s)
EPA
Description
The RERH specifications and checklists take a builder and a project design team through the steps of assessing a home’s solar resource potential and defining the minimum structural and system components needed to support a solar energy system.

* For non-dated media, such as websites, the date listed is the date accessed.

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Pacific Northwest National Laboratory

Last Updated

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.