Pentair ETi® 400 High Efficiency Natural Gas Heater 400K
The Pentair ETi® 400 High Efficiency Natural Gas Heater 400K brings you direct-fire pure titanium construction with the toughest ASME-certified heat exchanger ever built. At 96% thermal efficiency, the ETi 400 delivers the highest efficiency ever built in its class — all in a heater that operates at an ultra-quiet noise level and outperforms energy emissions standards.
Built by Pentair with a direct-fire pure titanium heat exchanger, cupro nickel housing, 400,000 BTU natural gas output, and a flow range of 40–120 GPM. Backed by a best-in-class 3-year parts and labor warranty.
⚠️ Professional Installation Required. Pool heater installation involves gas line connections and electrical wiring. Always use a licensed contractor to ensure safety, code compliance, and warranty validity.
Key Features
96% Thermal Efficiency
The highest efficiency ever built in the 400K BTU class — significantly more efficient than standard pool heaters.
Direct-Fire Pure Titanium Heat Exchanger
ASME certified — the toughest heat exchanger ever built for a pool heater. Superior corrosion resistance.
400,000 BTU Natural Gas
Maximum-capacity heating for large pools and spas.
Ultra-Quiet Operation
Designed for exceptionally quiet operation — won't intrude on poolside leisure.
Outperforms Energy Emissions Standards
Green certified — exceeds current energy and emissions standards.
Cupro Nickel Housing
Corrosion-resistant cupro nickel housing for long service life in any environment.
ASME Certified Construction
Built to the most rigorous pressure vessel standards in the industry.
3-Year Parts and Labor Warranty
The best warranty in its class — 3 full years of parts and labor coverage.
Who It's For
- Pool and spa owners who want the highest efficiency 400K BTU natural gas heater on the market
- Salt water pool owners and those with chemically demanding water chemistry
- Anyone who wants ASME-certified titanium construction and a 3-year parts and labor warranty
- Indoor and outdoor installations where maximum efficiency and ultra-quiet operation matter
Specifications
Heating Performance
| BTU Output | 400,000 BTU |
| Thermal Efficiency | 96% |
| Fuel Type | Natural Gas |
| Flow Rate | 40–120 GPM |
Construction
| Heat Exchanger Material | Direct-Fire Pure Titanium (ASME Certified) |
| Housing Material | Cupro Nickel |
Installation
| Application | Indoor / Outdoor / Pool / Spa |
Physical
| Product Weight | 379 lb |
| Shipping Dimensions | 40 × 30 × 46 in |
Approvals & Warranty
| Certifications | ASME Certified |
| Energy Efficient | Yes (Green Certified) |
| Warranty | 3 Years (Parts & Labor) |
What's in the Box
- Pentair ETi 400 High Efficiency Natural Gas Heater
- Union Fittings
- User Manual
Warranty
The ETi 400 comes with a 3-year parts and labor manufacturer warranty from Pentair. Clearflow Pool Supply is an authorized Pentair dealer and will assist with any warranty service needed.
Downloads
- Product Brochure (PDF)
- Product Brochure Alt 2 (PDF)
- Product Brochure Alt 3 (PDF)
- Install Guide (PDF)
Frequently Asked Questions
What makes the ETi 400 different from other 400K BTU pool heaters?
The ETi 400 is in a class by itself at 96% thermal efficiency — compared to 83-84% for standard pool heaters. Its direct-fire pure titanium heat exchanger is ASME certified and provides unmatched corrosion resistance. It's also backed by a 3-year parts and labor warranty, vs. 1-2 years on most competitors. The trade-off is a significantly heavier unit (379 lb) due to the premium construction.
What does ASME certified mean for a heat exchanger?
ASME (American Society of Mechanical Engineers) certification means the heat exchanger was designed and built to meet the most rigorous pressure vessel standards in the industry. It ensures the exchanger can safely and reliably handle the pressures and temperatures involved in pool heating applications over a long service life.
Why titanium instead of cupro nickel for the heat exchanger?
Pure titanium has superior resistance to corrosion compared to cupro nickel — particularly in salt water, high-chlorine, and other chemically aggressive environments. While cupro nickel is excellent for most applications, titanium is the premium material choice for maximum longevity in the most demanding conditions.
Does this heater require professional installation?
Yes. Gas heater installation involves connecting to a natural gas supply line, electrical wiring, and proper venting. A licensed pool contractor or plumber must perform the installation to ensure safety, local code compliance, and warranty validity.
What size pool is the 400K BTU ETi suitable for?
As a general guideline, 400,000 BTU is typically suited for pools in the 30,000–50,000 gallon range depending on climate, desired temperature rise, and heat loss factors. A licensed pool professional can calculate the correct BTU requirement for your specific pool and location.