circular brass component with a central hole and a black rubber ring around its edge on a white background
rectangular yellow label with black text showing natural gas conversion details including orifice size and product number
small brass ring with black gasket and yellow rectangular label with black text and barcode on white background

Pentair Propane to Natural Gas Conversion Kit – 333 Model | Max-E-Therm | 77707-1421

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SKU:
77707-1421
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About This Item

The Pentair Propane to Natural Gas Conversion Kit (77707-1421) is the OEM replacement conversion kit for the Sta-Rite Max-E-Therm 333 propane pool and spa heater — converting the burner system from liquefied propane gas (LP) to natural gas (NG) operation.

IMPORTANT: KIT CONTENTS
This listing is for a kit that includes items 3 & 4 from the Max-E-Therm 333 burner assembly. This kit is not included with the heater and must be ordered separately when a fuel-source conversion is required.

IMPORTANT: LICENSED PROFESSIONAL INSTALLATION REQUIRED
Gas and electrical heater components must be serviced by a licensed pool professional or qualified HVAC technician. Do not attempt to service gas or high-voltage components without proper certification. Converting a heater between fuel types involves gas supply connections and burner orifice changes — improper installation creates a serious fire and carbon monoxide hazard.

This kit provides the components required to convert the Max-E-Therm 333 burner system from propane to natural gas operation. Because propane and natural gas operate at different supply pressures and require different orifice sizing, a dedicated conversion kit is required — the heater cannot be converted by field modification of existing components.

Specifications

Pentair Part Number 77707-1421
Part Name Propane to Natural Gas Conversion Kit – 333 Model
Kit Contents Includes items 3 & 4 (per Max-E-Therm 333 burner assembly diagram)
Conversion Direction Propane (LP) to Natural Gas (NG)
Heater Model Compatibility Max-E-Therm 333 LP
Quantity Kit

Fits Into

Brand Equipment Line Model / Part Number Notes
Pentair (formerly Sta-Rite) Max-E-Therm 333LP Propane to NG Conversion Kit for 333 Model. Not included with heater; order separately.

Compatibility is based on Pentair parts documentation and available OEM records. This is not an exhaustive list. For certainty, verify the part number in your equipment's manual or on the original part itself before ordering.

Poolaroo Pro Tip

Before ordering, confirm your heater's current fuel configuration by checking the rating plate on the heater cabinet — it will clearly state LP or NG. This kit is directional: LP to NG only. If you need to convert in the opposite direction (NG to LP), a different kit is required. Always have the conversion performed by a licensed professional and confirm your local gas utility requirements for natural gas supply pressure and line sizing before scheduling the work.

CALIFORNIA PROPOSITION 65 WARNING: This product can expose you to chemicals which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov.
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Pentair Pool Products and Parts

About Pentair Pool Products and Parts

Pentair is often considered the "gold standard" for pool professionals, and for good reason. Founded in 1966 (originally by five inventors making high-altitude balloons!), the company has evolved into the global leader in smart, sustainable water solutions. For the DIY homeowner, Pentair represents the intersection of rugged durability and silicon valley-tier technology. They pioneered the Variable Speed Pump revolution with the IntelliFlo®, saving American pool owners millions in energy costs. Today, their ecosystem focuses heavily on automation, allowing you to control your pump, heater, lights, and chemistry from a single app. While they are a favorite among professional builders, their "EC" (E-Commerce) line of equipment allows homeowners to access pro-grade technology with valid warranties for DIY installation.

Why We Trust Pentair Pool Products and Parts
Energy Efficiency Leaders: Recipient of the ENERGY STAR® Partner of the Year award for over a decade; their pumps are designed to pay for themselves in energy savings.

Smart Automation: The Pentair Home App and IntelliCenter systems offer best-in-class control over your pool ecosystem from anywhere in the world.

Professional Pedigree: The brand most often recommended and installed by pool builders for high-end residential pools.

Eco-Conscious: Dedicated to reducing water waste and energy consumption through "Green" technology innovations.

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