Corresponding exhaust pipes for water heaters are typically PVC, CPVC, or stainless steel, depending on the type and venting requirements of the heater.
Water heaters don’t use exhaust pipes – they use specialized venting systems to safely remove combustion gases. Choosing the right vent pipe is critical for safety and efficiency. This guide covers all vent types, materials, and installation requirements.
Types of Water Heater Venting Systems
Atmospheric Venting
Standard gas water heaters use natural draft venting. Hot exhaust rises through vertical metal ducts (B-vent) that must slope upward. These can be dedicated or shared with other appliances.
- Uses double-wall metal pipes (aluminum or galvanized steel)
- Requires proper draft and clearances
- Most affordable option but least efficient
Power Vent Systems
These units have electric blowers that push exhaust through PVC pipes. The blower provides flexibility in vent routing.
| Advantages | Disadvantages |
|---|---|
| Can use horizontal runs | Requires electrical outlet |
| PVC is cheaper than metal | Higher upfront cost |
| More installation options | Additional moving parts |
Direct Vent Systems
Sealed combustion units that pull air from outside through coaxial “pipe-in-pipe” vents. Ideal for tight spaces with poor ventilation.
Key Features:
- No indoor air used for combustion
- Reduces backdraft risks
- Can terminate through sidewalls
Vent Pipe Materials
Metal Vent Pipes
Required for atmospheric venting. Type B-vent is most common, with aluminum inner wall and galvanized outer wall.
PVC Vent Pipes
Approved for power vent and high-efficiency condensing units. Must be Schedule 40 PVC rated for at least 140°F.
Installation Requirements
Clearances
Maintain proper distances from combustibles:
- 1″ clearance for single-wall pipes
- 0″ clearance for B-vent and PVC
Termination
Vents must extend at least 12″ above roof or sidewall. Keep away from windows and intake vents.
Professional Installation
Always hire a licensed plumber. Improper venting can cause carbon monoxide poisoning. The right HVAC tools are essential for proper installation.
Common Venting Issues
Backdrafting
Caused by negative pressure or obstructions. Test with smoke pencil near draft hood.
Condensation
High-efficiency units may need special drains for acidic condensate.
Leaks
Check all joints and seams. Use approved sealants and proper slope.
Advanced Venting Options
Concentric Venting
Single-pipe solution with inner exhaust and outer intake. Provides clean installation with one penetration.
Common Venting
Multiple appliances can share one vent if properly sized. Requires professional calculation.
Maintenance Tips
- Inspect annually for blockages
- Check for corrosion or damage
- Verify proper draft
- Clean burner compartment
For commercial applications, consider high-efficiency power vent models with PVC venting options.
