Query: The plumbers roughed-in the plumbing for our new home. We opted for recirculating hot water for our tankless heater. How are these things plumbed for new construction?
Answer: In new construction, plumbing for a recirculating hot water system with a tankless water heater involves a few key steps to ensure efficiency and functionality:
Rough-In Plumbing:
Initial Setup: The rough-in phase begins after framing but before wall covering. Plumbers install the main water supply lines, drain lines, and vent stacks. For a recirculating system, this includes planning for the hot water loop.
Supply Lines: For a tankless heater, both cold and hot water supply lines are run to where the heater will be installed. This includes ensuring there's a main shut-off valve and possibly isolation valves for easier maintenance.
Recirculation System Installation:
Dedicated Return Line: A common method involves installing a dedicated return line for the hot water. This line runs from the furthest fixture back to the tankless water heater. This setup allows for the hot water to circulate continuously or on-demand back to the heater, keeping the water in the pipes hot. This system typically requires more planning and piping during the rough-in phase, as it involves adding an extra pipe.
Pump Placement: The recirculation pump is generally placed near the water heater on the return line to push the cooled water back into the heater for reheating. If a timer or on-demand system is used, this can be controlled to run only during peak usage times, saving energy.
Tankless Water Heater Considerations:
Positioning: The tankless heater should be placed in a location that minimizes the distance the hot water needs to travel to fixtures, which can be challenging in larger homes. However, with a recirculating system, this issue is mitigated since the water stays hot in the loop.
System Integration: Ensure that the tankless water heater can handle the constant demand of a recirculation system. Some tankless units have built-in recirculation features or are designed to work with external pumps. Check compatibility with your specific model.
Piping and Insulation:
Pipe Material: Use materials like PEX or copper for durability and efficiency, with PEX being popular due to its flexibility and ease of installation.
Insulation: Insulating the hot water pipes is crucial to reduce heat loss, especially in the recirculation loop, ensuring the water remains hot as it travels through the house.
Regulations and Testing:
Compliance: Ensure the installation complies with local building codes, particularly regarding energy efficiency and water conservation.
Testing: After installation, the system should be pressure tested to check for leaks, especially before covering the pipes with drywall or other finishes.
This setup ensures that hot water is available almost immediately at every fixture, reducing water waste and enhancing user convenience. However, remember that while a recirculating system with a tankless heater can be highly efficient, the initial setup and additional piping can increase costs and complexity.
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