Using a water column (manometer) to determine appropriate fuel pressure

A manometer (analog or digital) can be used to measure fuel pressure and confirm it is within the required range for the generator and fuel type.

Important: Fuel pressure testing should be performed by a qualified service professional, such as a Generac Independent Authorized Service Dealer (IASD), a licensed plumber, or your gas utility. This process may require specialized tools and involves working with fuel systems. Improper testing or adjustments can cause a no-start condition, unsafe operation, equipment damage, or personal injury.

Fuel pressure ranges

• Liquid propane (LP vapor): 10 to 12 inches of water column (0.36 to 0.43 PSI)
• Natural gas (NG): 3.5 to 7 inches of water column (0.13 to 0.25 PSI)

Note: Fuel pressure requirements are based on the generator model and fuel type, not the regulator or fuel inlet alone. Use the generator’s documentation to verify requirements for your specific product. See How do I find a copy of my home standby generator owner’s manual and spec sheets?

Next Generation Series vs. Guardian Series testing

The process for testing fuel pressure is not the same for all home standby generators. Next Generation Series and Guardian Series generators can use different test points, setup steps, and acceptance criteria depending on the model and installation configuration.

To ensure correct and safe testing, have your Generac IASD, licensed plumber, or gas utility follow the fuel pressure test procedure outlined in the installation manual for your specific generator. Installation manuals can be located using the installation manual guidance, or by using the product lookup page.

Why fuel pressure matters

• If fuel pressure is too low, the generator can be starved for fuel and may not start, may run rough, or may not be able to support load.
• If fuel pressure is too high, the fuel system components may not operate correctly and the generator may not start. Excessive fuel pressure may contribute to component damage.

Get help from a qualified professional

If you suspect a fuel pressure issue, contact a qualified service professional rather than attempting to test or adjust fuel pressure yourself.

• To understand what an IASD is, see What is a Generac Independent Authorized Service Dealer (IASD)?
• To find a local Generac service dealer, see How can I find a Generac service dealer in my area? or use the dealer locator.

See also

• Troubleshooting low fuel pressure issues in air-cooled home standby generators
• What is the maximum pressure that should be supplied to the generator’s demand regulator?
• How do I determine the fuel line sizing for my air-cooled home standby generator?