Pentair Max-E-Therm® Liquid Propane Pool & Spa Heater 400K BTU
The Pentair Max-E-Therm® Liquid Propane Pool & Spa Heater 400K BTU lets you save money and energy without compromise. Already known for dependability and efficiency, the Max-E-Therm now offers smart features and an optional energy-saving automatic bypass to help ensure your pool is ready whenever you are.
Built by Pentair (Sta-Rite) with an 84% efficiency rating — rated first in its class — the Max-E-Therm 400 LP features a lightweight, compact Dura-Glas® rustproof matte black enclosure, Low NOx certification, and direct compatibility with Sta-Rite System:3 Mod Media filters. Liquid propane version for locations without natural gas access. CSA certified for indoor and outdoor use. Backed by a 2-year warranty.
⚠️ Professional Installation Required. Pool heater installation involves propane gas line connections and electrical wiring. Always use a licensed contractor to ensure safety, code compliance, and warranty validity.
Key Features
400,000 BTU Liquid Propane — 84% Efficiency
Highest efficiency in its class for LP pool heaters — ideal for locations without natural gas.
Lightest Heater in Its Class
Lightweight design makes installation easier and reduces labor costs.
Compact Retrofit Design
Ideal for retrofit installations where space is limited on an existing equipment pad.
Optional Automatic Bypass
Energy-saving automatic bypass option to optimize operating costs.
Easy Gas Source Switching
Convert between LP and natural gas with installation of a separate orifice.
Dura-Glas® Rustproof Housing
Sleek matte black enclosure resists rust and corrosion for long service life.
Low NOx — Environmentally Friendly
All units are Low NOx certified.
Sta-Rite System:3 Compatible
Direct-connects to Sta-Rite System:3 Mod Media filter or fits other systems easily.
Indoor and Outdoor Certified
CSA certified for both indoor and outdoor pool and spa installations.
2-Year Warranty
Pentair residential warranty coverage.
Who It's For
- Pool and spa owners without natural gas access who want the highest efficiency 400K BTU LP heater
- Retrofit installations where a compact, lightweight heater is essential
- Sta-Rite System:3 filter owners who want direct heater integration
- Anyone who may want to switch between LP and natural gas in the future
Specifications
Heating Performance
| BTU Input | 400,000 BTU |
| Thermal Efficiency | 84% |
| Fuel Type | Liquid Propane (convertible to NG) |
| Emissions | Low NOx |
| Flow Rate | 40–120 GPM |
Construction
| Enclosure | Dura-Glas® (Rustproof, Matte Black) |
| Control Type | Digital |
Installation
| Voltage | 120V / 240V |
| Frequency | 60 Hz |
| Phase | Single |
| Application | Indoor / Outdoor / Pool / Spa |
Physical
| Product Weight | 138 lb |
| Cabinet Dimensions | 25.15 W × 30 D × 26 H in |
| Shipping Dimensions | 27.75 × 34.25 × 32 in |
Approvals & Warranty
| Certifications | CSA Certified |
| Energy Efficient | Yes (Green Certified) |
| Warranty | 2 Years |
What's in the Box
- Pentair Max-E-Therm 400 Liquid Propane Pool & Spa Heater
- Union Fittings
- User Manual
Warranty
The Max-E-Therm 400 LP comes with a 2-year manufacturer warranty from Pentair. Clearflow Pool Supply is an authorized Pentair dealer and will assist with any warranty service needed.
Downloads
Frequently Asked Questions
What is the difference between this and the Max-E-Therm 400 NG (SR400NA)?
The SR400LP runs on liquid propane and the SR400NA runs on natural gas. All performance specifications — BTU output, thermal efficiency, Dura-Glas housing, and warranty — are identical. Choose the LP model if you don't have natural gas service at your property. Both can be converted to the other fuel type with a separate orifice kit.
Does this heater require professional installation?
Yes. Propane heater installation involves connecting to a propane 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 is the automatic bypass option?
The optional automatic bypass diverts flow around the heater when it's not actively heating, reducing hydraulic resistance and lowering pump energy consumption — an energy-saving add-on for efficiency-focused installations.
What size pool is the 400K BTU 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.
Can it be used indoors?
Yes. The Max-E-Therm is rated for both indoor and outdoor installation. Indoor propane installations require proper venting per local code. Consult the install guide and a licensed contractor for indoor venting requirements specific to propane appliances.