Yes, PEX can be used directly from an electric water heater for hot water supply, ensuring proper fittings and temperature ratings are adhered to.
Connecting PEX tubing directly to an electric water heater is a common question among homeowners and plumbers. While PEX offers flexibility and cost savings, there are important factors to consider before making this connection.
PEX and Electric Water Heaters: The Basics
PEX (cross-linked polyethylene) tubing has become popular for plumbing due to its flexibility, durability, and lower cost compared to copper. When it comes to electric water heaters, the rules differ from gas models.
Manufacturer Specifications Matter Most
Most electric water heater manufacturers allow direct PEX connections if their installation manual permits it. For example, Rheem’s installation guide specifically mentions PEX as an acceptable connection method. Always check your heater’s manual first.
Temperature Considerations
Electric water heaters typically operate at 120-140°F, well below PEX’s maximum temperature rating of 180-200°F. This makes them safer for direct PEX connections than gas models with hot exhaust vents.
Code Requirements for PEX Connections
Plumbing codes vary by location, but most don’t prohibit direct PEX connections to electric water heaters. The key factors are:
- No national code requires 18″ of copper for electric heaters (unlike gas)
- Local codes may have specific requirements
- Manufacturer instructions override code in most cases
Zurn PEX Installation Guidelines
According to Zurn’s installation guide, PEX can connect directly to electric water heaters for residential applications. They recommend using brass threaded adapters for best results.
Best Practices for PEX Water Heater Connections
Even when allowed, follow these professional tips:
- Use PEX-A tubing for better heat resistance
- Install dielectric unions to prevent corrosion
- Leave some slack for expansion/contraction
- Support pipes properly near connections
When to Use Metal Connectors
Some situations still call for metal connectors:
- If manufacturer requires it
- For commercial applications
- When local code mandates it
- With tankless electric heaters (higher temps)
Comparing PEX to Other Connection Methods
| Material | Cost | Installation | Electric Heater Compatibility |
|---|---|---|---|
| PEX | $$ | Easy | Usually allowed |
| Copper | $$$$ | Moderate | Always allowed |
| CPVC | $$ | Easy | Often allowed |
| Stainless Flex | $$$ | Very Easy | Always allowed |
Potential Issues With Direct PEX Connections
While generally safe, be aware of these possible concerns:
Temperature and Pressure Valve Discharge
The T&P valve releases water at 210°F when triggered, which exceeds PEX’s rating. This is why some pros recommend at least 12″ of metal pipe for the discharge line.
Expansion and Contraction
PEX expands more than metal when heated. Use proper supports and allow for movement to prevent stress on connections. Consider using a flexible connector if needed.
Professional Recommendations
Most licensed plumbers suggest:
- Direct PEX connections are fine for residential electric heaters
- Use quality brass fittings (not plastic)
- Follow all local codes and manufacturer specs
- Consider stainless steel flex connectors for easiest installation
For complex installations or commercial jobs, consult a professional. The right tools and experience make all the difference in plumbing work.
Final Verdict
In most cases, yes – PEX can connect directly to an electric water heater when the manufacturer approves it and local codes allow. Always verify these requirements before proceeding with your installation.
