Product Overview

The Raypak 018758F UG (Unitherm Governor) Bypass Assembly Kit is a genuine OEM replacement component designed for select Raypak gas pool and spa heaters.

The bypass assembly regulates internal water flow and temperature through the heater's heat exchanger. Proper bypass operation helps maintain balanced flow, efficient heat transfer, and protection against excessive thermal stress. The 018758F is commonly cataloged for Raypak 336-408 heater applications, with exact compatibility dependent on heater series, model, and production date.

Key Features

Genuine Raypak OEM Replacement
Factory-authorized replacement assembly manufactured for compatible Raypak pool and spa heaters.

Unitherm Governor / Bypass Assembly
Combines temperature-responsive governor and bypass functions to regulate water movement through the heat exchanger.

Supports Proper Heater Flow
Helps maintain appropriate internal water flow for consistent heater performance.

Temperature-Regulated Operation
The Unitherm Governor responds automatically to water temperature to help maintain proper heat-exchanger operating conditions.

Complete Service Assembly
Designed as a replacement assembly for worn, stuck, damaged, or malfunctioning bypass components.

Benefits

• Genuine Raypak OEM replacement part
• Helps restore proper heater water flow
• Supports consistent heat-transfer performance
• Helps protect the heat exchanger from thermal stress
• Automatic temperature-responsive operation
• Ideal for professional heater repair and maintenance
• Allows bypass-system repair without replacing the complete heater

Specifications

Installation Information

Installation requires access to the heater's water-header and bypass assembly. Shut off electrical power and gas to the heater and allow the unit to cool before beginning service.

Inspect the surrounding header, O-rings, bypass components, Unitherm Governor seating surfaces, and related hardware while the assembly is removed. Sealing surfaces should be clean and undamaged before installing the replacement.

Pool and spa gas-heater repairs should be performed by a qualified service professional.

Confirm Before Ordering

Raypak 018758F is commonly sold as the UG Bypass Assembly Kit 336-408, but heater generation is important when determining exact compatibility.

Current Raypak replacement-parts documentation specifically identifies 018758F for certain 337A and 407A Low NOx heaters manufactured from December 2019 forward. Other Raypak 336A/406A Atmospheric configurations may use 018759F instead.

Always confirm:

• Heater model
• Heater series
• Serial number
• Low NOx vs. Atmospheric configuration
• Existing bypass assembly part number
• Manufacturing date

before ordering.

Warranty Information

Raypak identifies genuine factory-authorized heater kits and accessories as certified and warranted replacement components. Exact warranty duration for 018758F should be confirmed under Raypak's current replacement-part warranty terms at the time of purchase.

Customer Q&A

Q: What does the Raypak 018758F do?
It regulates internal water flow and temperature through the heater's heat exchanger.

Q: Is this a genuine Raypak part?
Yes. The 018758F is a genuine Raypak OEM replacement assembly.

Q: Does it fit every Raypak 336 or 408 heater?
No. Compatibility varies by heater series, Low NOx/Atmospheric configuration, and production date. Verify the exact heater before ordering.

Q: Is the Unitherm Governor part of the assembly?
The 018758F is identified as a UG/Bypass assembly and incorporates the temperature-responsive governor/bypass function.