How to Install Two Water Heaters in Parallel: A Complete Guide.

To install two water heaters in parallel, connect both units to a common set of pipes and electrical circuits. In other words, install them side-by-side, using the same inlet and outlet pipes and electrical wiring as well as maintaining consistent water temperature.

Installing two water heaters in parallel has many benefits for homeowners, including faster hot water recovery time and increased capacity for larger households. However, the process can be challenging and should only be undertaken by experienced individuals. In this article, we will provide step-by-step instructions on how to install two water heaters in parallel, including a list of necessary tools, safety precautions, and tips for ensuring a successful installation.

By following our guide, you can enjoy all the benefits of parallel water heaters without incurring additional costs or complications.

How to Install Two Water Heaters in Parallel: A Complete Guide.


Preparing For Installation

Installing two water heaters in parallel can be a great solution for households with high hot water demand. Before starting the installation process, there are a few things to consider. Here are some key points to help you prepare for the installation:

Assessing Power Supply Requirements

  • Check your electrical panel to ensure that it can provide enough power for two water heaters. Each water heater will require its dedicated 220-240v circuit and 30-amp breaker.
  • Hire a certified electrician to verify the power supply requirements and installation process.

Measuring The Space And Selecting The Location

  • Measure the space where you plan to install the water heaters. Make sure there is adequate space for the two water heaters and any related plumbing such as supply and discharge pipes.
  • Select a location that is suitable for the two water heaters. Consider accessibility, drainage, and ventilation requirements.

Gathering Necessary Tools And Materials

  • Make a list of all the necessary tools and materials required for the installation process. This will depend on your plumbing system and the water heaters you are installing.
  • Some essential tools and materials include pipe wrenches, tubing cutters, flexible connectors, shut-off valves, teflon tape, and pipe fittings.
READ MORE  Don't Let Hard Water Bog Down Your AO Smith: How Often Should You Flush It?

Ensure Compliance With Local Building Codes And Safety Guidelines

  • Check with your local building codes and safety guidelines to ensure compliance with installation requirements and safety standards.
  • Hire a certified plumber or contractor to carry out the installation process to ensure it meets all local codes and regulations.

By following these crucial steps, you can ensure that your installation process runs smoothly and without any complications. It’s crucial to keep safety in mind and always hire certified professionals where necessary.

Installing The Water Heaters

Installing Two Water Heaters In Parallel: A Complete Guide

If your household has high water consumption, you may consider installing two water heaters in parallel. By doing so, you can enjoy uninterrupted hot water supply and avoid running out of hot water during peak hours. Here’s a complete guide on how to install two water heaters in parallel.

Mounting The Water Heaters

Before mounting your water heaters, you need to ensure that the location you choose is suitable and has enough space to fit them. Here are the key points to keep in mind when mounting the water heaters:

  • Choose a location with easy access to both water heaters.
  • Ensure the location is on a level surface to prevent any wobbling.
  • Leave enough space between the water heaters for maintenance purposes.
  • Install a metal stand or shelf to provide sturdy support for the heaters

Connecting The Water Heaters

Now that your water heaters are mounted, the next step is to connect them in parallel to ensure optimal functioning. Here are the key points to keep in mind when connecting the water heaters:

  • Use union fittings to connect both the hot and cold water lines to each water heater.
  • Install a shut-off valve for each water heater.
  • Use flexible hot water connectors to connect the water heaters.
  • Install a backflow prevention device to prevent cross-connection between the water heaters.
  • Connect each water heater to the gas line.

Wiring The Water Heaters

Proper wiring is crucial when installing two water heaters in parallel to ensure they function correctly and safely. Here are the key points to keep in mind when wiring the water heaters:

  • Connect both water heaters to a dedicated 240v circuit.
  • Use appropriate wires of the right length, size, and type for wiring.
  • Keep the wires well-organized and labeled.
  • Use a double-pole circuit breaker for the 240v circuit.
READ MORE  How To Tell If Water Heater Breaker Is Off?

By following these steps, you can efficiently and safely install two water heaters in parallel and enjoy continuous hot water supply. Remember that proper installation is critical to ensure your water heaters function correctly and efficiently for years to come.

Testing And Troubleshooting

If you’re planning to install two water heaters in parallel, testing and troubleshooting are crucial steps to ensure that your project is working efficiently. By doing so, you can save yourself from costly repairs and potential damage to your home.

In this section, we will delve into the essential steps you need to follow to test the water heaters and troubleshoot any common issues that may arise during installation.

Testing The Water Heaters

To test the water heaters in parallel, you should follow these steps:

  • Turn off the electricity or gas supply to the water heaters before you begin testing.
  • Turn on the cold water supply and let the tanks fill completely.
  • Once the tanks are full, turn on the electricity or gas supply.
  • Set the temperature of each tank to the same level. Ensure that the thermostat readings of both water heaters are accurate. If you notice any issues with the thermostat, replace it.
  • Turn on the hot water supply of both tanks and wait for some time. Check the temperature of the water coming out of both tanks. It should be at the same temperature.
  • Test the pressure relief valve of each tank by lifting the valve lever. Water should flow out of the valve and stop once you release the lever. If there is no water flowing, replace the valve.
READ MORE  Where To Dump Old Water Heater?

Troubleshooting Common Issues

Installing two water heaters in parallel can be a complex task. However, various issues may arise during or after installation, which you need to troubleshoot. Here are some of the common issues and how to resolve them:

  • If there is no hot water from either tank, check if the circuit breaker is on and if the thermostat is working correctly.
  • If the temperature of the water is too high, check the thermostat settings and adjust them accordingly.
  • If there is an unusual noise, it could be due to sediment build-up. Drain the tanks to remove the sediment.
  • If you notice a leak, turn off the water supply and check the connections for any loose parts. Tighten any loose connections and replace any damaged parts.

Testing and troubleshooting your water heaters is an essential step to ensure your installation is successful. By following these steps, you can minimize the chances of costly repairs and prolong the lifespan of your water heaters. Remember to contact a professional if you encounter any issues that you cannot handle yourself.


As we come to the end of our guide on how to install two water heaters in parallel, it is clear that this process is simple and straightforward. By following the steps outlined above, you can increase your water heating capacity and enjoy hot water at all times.

Remember to hire a qualified professional for the job and ensure that all safety measures are taken during installation. It is also important to keep in mind the importance of proper maintenance and regular inspections to ensure the longevity and efficiency of your water heaters.

Taking these precautions will not only ensure that your water heating needs are met, but it will also save you money in the long run. We hope that this guide has been helpful and informative in addressing any questions or concerns you may have had about installing two water heaters in parallel.


I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.