Maxitrol Gas Regulators – Gas Line Pressure vs Appliance Control

 In Gas Regulators, Maxitrol

Line pressure regulator vs appliance regulator? Can an appliance model serve as a line pressure regulator? Alternatively, can a line pressure unit serve as an appliance regulator? Are you confused by line pressure and appliance regulator standards?

Recently, it became clear that a customer was using an appliance regulator as a line pressure regulator, and they were not conforming to standards. Here is the reader’s digest version of the rules and how they apply to Maxitrol gas regulators.

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Line Pressure Regulator vs Appliance Regulator Standards

The current standards for appliance regulators are ANSI Z21.18/CSA 6.3, while line pressure regulator standards are ANSI Z21.80/CSA 6.22. Historically, appliance regulators were used as line pressure regulators before ANSI Z21.80/CSA 6.22 existed. With the implementation of the newer and revised standards, appliance regulators should no longer be used as line pressure regulators. This rule has been confusing given that many longtime favorite appliance regulators were used as line pressure regulators.

The standards apply to natural gas, manufactured and mixed gases, liquefied petroleum gases, and LP gas-air mixture systems.

line pressure regulator vs appliance regulator maxitrol gas regulators 325-L SeriesMaxitrol Appliance Regulators

The Maxitrol RV Poppet Series, RV Straight-Thru-Flow Series, and RS Balanced Valve Series are certified ANSI Z21.18 as appliance regulators and rated for a maximum inlet pressure of ½ PSI with outlet pressures being 2.8″ or 3″ to 12″ WC.

Maxitrol’s 325 Series regulators (325-3, 325-5, 325-7A, 325-9, and 325-11) are also certified ANSI Z21.18/CSA 6.3 as appliance regulators for the main burner or pilot applications with a maximum inlet pressure of 5 PSI (CSA certified).

The same Maxitrol 325 Series has an “L” line, denoting that the “L” regulators are certified as line pressure regulators to supply gas pressure to one or more appliances downstream. (325-3L, 325-5L, 325-7AL, 325-9L and 325-11L)

Line Pressure Regulators

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We use line pressure regulators in a building’s gas distribution system and install them between the service regulator and the gas appliance’s pressure regulator.

Maxitrol’s 325-L Series line pressure regulators are certified ANSI Z21.80/CSA 6.22 in 2 PSI and 5 PSI systems [when installing with an overpressure protection device (OPD)]. The L-Series regs are for CSST (corrugated SS), semirigid copper pipe, or steel/black iron pipe. The regulators reduce the pressure to a level within the appliances operating supply range. Install the line pressure regulator upstream of devices already fitted with an appliance regulator.


The Maxitrol 325 L-Series line pressure regulators are certified for 2 PSI inlet pressure, with outlet pressures ranging 7 to 11 inches WC. The 325-L Series regulators in 2 PSI systems deliver positive dead-end lockup capable of precise control from full flow down to pilot flow, suggesting that one 325-L would suffice as both line pressure and appliance regulator.


At supply pressures above 2 PSI, the ANSI Z21.80/CSA 6.22 standard requires an overpressure protection device that is factory assembled, approved, and tested for use with the regulator to limit the downstream pressure to 2 PSI maximum in the event of line regulator failure.

The Maxitrol 325 L-Series with an overpressure protection device (OPD) is certified for up to 5 PSI inlet pressure and outlet pressures ranging from 7 to 11 inches WC.

In a 5 PSI system, the user would need a second appliance regulator (RV Series or 210 with vLimiter) in series with the 325-L regulator (with OPD). The following factory-assembled 325-L line regulator with OPD will work:

Line Size Maxitrol 325-L Description
½” 325-3L48 Line Regulator with OPD
¾” or 1″ 325-5L600 Line Regulator with OPD
1-1/4″ or 1-1/2″ 325-7AL210D Line Regulator with OPD
1-1/2″ or 2″ 325-9L210E Line Regulator with OPD










Options for Line Pressure Control

Up to 7 PSI Systems

For high flow and input pressures up to 7 PSI, consider the Dungs FRS 7../6 line pressure regulators with internal vent limiters.

Vent Limiting Device

The Maxitrol vLimiter is a vent limiting device that eliminates the need to vent to an exterior wall. When using the vLimiter, install the regulator in a horizontal upright position, and if there is a diaphragm rupture, the gas escapement is within ANSI standard requirements.

Vent Protectors

The Maxitrol vProtector is for outdoor applications of Maxitrol units. Install the vent protector on the vent opening to protect the breather hole from the elements and debris.

If you are interested in Maxitrol, submit your inquiry to the request for information or call us at (303) 697-6701.

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General Video on Regulators

Image by Сергей Горбачев from Pixabay

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  • Avatar
    Steve Watt

    WE are opening a new building serviced with a 2 lb pressure of natural gas.We have need of regulators inside for (8) radiant tube heaters at 200,000 BTU’s each. We also need (2) outdoor regulators for Make up heaters at 1,071,947 BTU’s (7in – 14in WC) each
    Please quote these to us.
    Steve Watt
    Midwest Cooling Towers
    Chickasha OK 73023
    Cell: 405-834-0415
    Work: 405-222-6659

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