Proper venting is crucial for any gas tankless water heater. Without it, dangerous gases can build up in your home, and your heater may not run efficiently—or safely. If you’re planning to install a new tankless unit or replace an old venting system, this step-by-step guide covers everything you need to know: the main venting options, key installation rules, safety tips, top vent kits, and common questions. Get peace of mind, protect your investment, and ensure safe, reliable hot water year-round.
Quick Picks: Best Tankless Water Heater Vent Kits & Supplies
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Best Overall:
Rinnai 223176PP Condensing Horizontal Termination Kit – Complete kit for most Rinnai and compatible condensing models. -
Best for Vertical Roof Vent:
Noritz VP4-45VN PVC Vent Pipe Kit – Durable, easy to install, and code-approved for vertical runs. -
Best Budget:
Eccotemp Horizontal Stainless Steel Vent Kit – Affordable, simple, and fits many standard gas tankless heaters.
Venting Basics: Why & How Tankless Water Heaters Are Vented
- Gas tankless water heaters (natural gas or propane) must vent combustion gases outdoors for safety.
- Venting also supplies fresh air for combustion, improving efficiency and reducing carbon monoxide risk.
- Electric tankless heaters do not require venting.
- Venting can be run horizontally (side wall), vertically (roof), or even using direct vent/concentric pipe systems that handle intake and exhaust in one pipe.
- Always use vent pipe and kits certified for your heater model and local code.
Types of Tankless Water Heater Venting
- Direct Vent (Concentric): One pipe inside another—brings in fresh air and vents exhaust with a single wall or roof opening. Most modern condensing heaters use this.
- Single Pipe (Non-condensing): Older or budget models may vent exhaust only—requires separate intake air.
- Materials: Use stainless steel (Category III) for non-condensing units (hot exhaust), and PVC/CPVC for condensing units (cooler exhaust).
Step-by-Step: How to Vent a Tankless Water Heater
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Read the Manual & Check Local Code
Venting rules and approved materials can vary by location and heater model. Always follow manufacturer’s instructions. -
Plan the Vent Route
Short, straight runs are best. Avoid sharp bends and limit total length per the manual. Choose a clear route—either through an outside wall (horizontal) or roof (vertical). -
Mark and Cut the Wall or Roof Opening
Use the vent kit’s template to mark. Drill a pilot hole, then cut with a hole saw or reciprocating saw. Check for wires/pipes before cutting. -
Install the Vent Pipe
Start at the heater and work outward. Secure each section with approved clamps or gaskets—no screws inside the vent (can catch condensation or exhaust). Slope horizontal runs slightly back toward the heater for condensation drain. -
Attach Termination Cap/Kit
Mount the exterior vent cap per kit instructions. Caulk or seal around the opening for weatherproofing. -
Connect Fresh Air Intake (if needed)
For direct vent, connect the intake pipe to the proper collar. For single vent, ensure room has enough air supply or add an intake vent as required. -
Test Operation & Check for Leaks
Start the heater and check for exhaust leaks, proper airflow, and any error codes. Check local requirements for inspection.
Tip: If you’re not comfortable cutting vent holes or working with gas, always hire a licensed installer. DIY is possible for handy homeowners but must meet all safety codes.
Buyer’s Guide: Choosing the Best Tankless Water Heater Vent Kit
- Compatibility: Use vent kits approved for your heater model/brand (Rinnai, Noritz, Rheem, Navien, etc).
- Material: Stainless steel (Category III) for non-condensing, PVC/CPVC for condensing.
- Route: Choose horizontal or vertical kit based on your wall/roof access.
- Length: Measure the full route—most kits are 3–5 feet, with extension options if needed.
- Weather Protection: Look for vent caps with screens, bird guards, and rain shields.
- Code Approval: Only use kits marked for gas water heater use—never substitute generic ducting or dryer vent hose.
Product Reviews: Top Vent Kits & Supplies
Rinnai 223176PP Condensing Horizontal Termination Kit
- Concentric vent (intake & exhaust in one)
- Approved for Rinnai and many major condensing brands
- Includes termination cap, pipe, and all mounting hardware
Final Verdict: The best kit for most wall-vented condensing tankless heaters.
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Noritz VP4-45VN PVC Vent Pipe Kit
- Ideal for vertical/roof installs with condensing models
- Durable, UV-resistant, and code compliant
- Includes cap, pipe, and adapters
Final Verdict: Top choice for roof-vented condensing heaters.
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Eccotemp Horizontal Stainless Steel Vent Kit
- Compatible with many non-condensing gas tankless heaters
- Category III stainless steel for high-temp exhaust
- Affordable, easy to install, and weatherproof
Final Verdict: The best budget kit for standard wall venting.
See details on Amazon
Comparison Table: Best Tankless Water Heater Vent Kits
| Kit | Material | Type | Length | Compatible Brands | Price Link |
|---|---|---|---|---|---|
| Rinnai 223176PP | PVC/Polypropylene | Concentric/Horizontal | 3–5 ft | Rinnai, compatible condensing | View |
| Noritz VP4-45VN | PVC | Vertical | 4.5 ft | Noritz, condensing | View |
| Eccotemp Vent Kit | Stainless Steel | Horizontal | 3 ft | Eccotemp, compatible non-condensing | View |
FAQ: Venting a Tankless Water Heater
- Can I use PVC pipe for venting?
Only for condensing units (low-temp exhaust). Non-condensing units require stainless steel (Category III) venting. - Can I vent a tankless heater into an old chimney?
Only if the chimney is relined with an approved vent pipe—never use brick/masonry alone. - Does my electric tankless water heater need venting?
No—electric models don’t burn fuel and do not require venting. - How close can the vent be to windows or doors?
Follow your local code—usually at least 12–24 inches from any opening. - What if I smell gas or exhaust inside?
Turn off the heater, ventilate the area, and call a professional immediately.
Conclusion
Safe, proper venting is essential for any gas tankless water heater. Choose a vent kit rated for your heater, follow the step-by-step install tips above, and always check your local code for extra safety. For most homeowners, a concentric direct vent system is the easiest and safest option. Ready to get started? Check the top vent kits above, and enjoy reliable, efficient hot water with total peace of mind!