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Vent-O-Mat - RGXII - Air Release Valves

Deeco - Vento-O-Mat - Product Image
Brand: Vent-O-Mat
Category: Air Valves, Wastewater Combination Air Valves
Size Range:



50mm - Threaded Female BSPT

80-200mm - Flanged AS4087 - PN16

Product Description

The Vent-O-Mat Series RGXII "Anti-Surge" sewage air release and vacuum break valve, is an evolution of market feedback and the incorporation of the already proven Vent-O-Mat technology resulting from years of extensive research. The valve unlike many others is not just an adaption of an air valve to handle sewage, but the result of over 30 years of dealing with sewage and seeing what works and adapting it to the needs of the end user.

Features & Benefits

  • High-capacity air discharge during pipeline filling
  • High volume air intake for vacuum break purposes, both during draining of water pipelines and/or column separations
  • Independent third-party tested
  • Controlled pressurized air discharge releases air when pipelines are fully charged.
  • Surge relief prevents pipeline bursts during pump trips & rapid pipeline filling.
  • More compact & shorter to accommodate existing installations and retrofits.
  • Designed for low head sealing where line pressures are generally lower than normal.

“Anti-Shock" - "Anti-Surge"-

The RGXII is an air release valve that is supplied as standard with a mechanism to prevent pipeline damage from the high-induced pressure transients associated with high-velocity air discharge. The surge resulting from liquid column separation and liquid oscillation is dramatically reduced as an automatic function of this mechanism. This same mechanism allows for controlled filling of the pipeline, maintaining controlled discharge at all times.


The RGXII is more compact and shorter without compromising the pressure rating of the valve.

Full Port Opening on Negative Pressure -

During pipeline draining and instances of surge, the valve will allow the intake of air to the full nominal bore of the valve. The RGXII series large orifice diameter equals the nominal size of the valve, i.e., an 8" valve has an 8" orifice. This ensures the least possible resistance to the intake of air and consequently the least possible negative pressure within a draining pipeline.

Sealing -

The RGXII has been designed for low-head sealing as well where line pressures are

generally lower than normal.

Material -

The RGXII is now available with a fusion-bonded Ductile Iron Body as well as a 304

or 316 Stainless Steel Body.

Performance -

The RGXII has been designed and developed to provide the optimum usable

and safe performance relative to all functions.

Quality -

The RGXII economically offers the highest quality construction and materials available in an air release and vacuum break valve. Stringent manufacturing and test procedures are maintained to ensure the best possible service and reliability is given by every valve produced.

Serviceability -

The RGXII design facilitates extreme ease of service and maintenance. Components are in corrosion-free materials to allow problem-free disassembly and reassembly even after many years of operation. All maintenance spares are replaceable without special tools or skills.

Available Configurations

  • Standard – 4 functions
  • Biased
  • Flanged/Threaded Outlet

Typical Applications

Surge Protection-Initial Filling

The RGXII is always biased in the "Anti-Surge" mode meaning all air release is controlled through the “Anti-Surge” Orifice which is aerodynamically engineered to throttle air discharge when liquid approach velocity would otherwise become too great and induce an unacceptable pressure rise. The air throttling action increases resistance to the flow of the approaching liquid which consequently decelerates to a velocity that reduces the pressure rise when the valve closes (see operation below). Vent-O-Mat series RGXII is an essential precaution for pipeline priming.

Surge Protection - Pump Trip Conditions

In instances where a pipeline experiences liquid column separation due to pump stoppage, high shock pressures can be generated when the separated liquid column rejoins.

The Vent-O-Mat series RGXII takes in air through the unobstructed large orifice when liquid column separation occurs but controls the discharge of air/gas through the "Anti-Surge" Orifice as the separated column commences to rejoin. The rejoining impact velocity is thereby considerably reduced to alleviate high surge pressures in the system (see operation)

Other surge control measures may, dependent on pipeline profile, diameter, and operating conditions, be needed to provide the primary surge alleviation function with the Vent-O-Mat sewage air valves forming an integral and valuable addition in a combined strategy for further reducing surge pressures. The benefit of the "Anti-Surge" Orifice can be readily demonstrated by suitable surge modeling software.

Surge Protection - Pipeline Operating

The operation of valves and similar flow control devices can cause high-pressure transients in an operating pipeline. The unique, single-chamber design of the Vent-O-Mat series RGXII valve enables a pocket of air to be trapped in the valve.

chamber. The automatic operation of the small orifice control float regulates the volume of air entrapped. The volume maintained in the valve will provide a cushioning benefit to the pipeline for short-duration transient pressure "spikes". This effect can be modeled by the design engineer using suitable surge software.

Computer Modelling

The effectiveness of Vent-O-Mat “Anti-Surge” technology has been substantiated by independent third-party testing and by thousands of applications globally. Effective computer modeling, based on practical tests, has been ensured in the well-known and respected commercially available surge analysis software programs such as AFT impulse, FLOWMASTER, Waltham, and SURGE 2000.

Technical Data



RGX2-Operation 1

Air/gas flows through the annular area around the control float assembly and to the atmosphere through the anti-surge float and out the large orifice.


RGX2-Operation 2

Sewage/effluent has entered the valve chamber and buoyed the floats to close both the large and the small orifice. The design's compression/ volume relationship prevents the media from ever exceeding the maximum surge level indicated above. The resultant sewage/effluent-free area protects against the fouling of the orifice seals by solids or highly viscous substances.


RGX2-Operation 3

The volume of distrained air/gas increases in the valve, displacing the sewage/effluent below the normal operating level. This results in the control float dropping away from the small orifice. The pressurized air/gas is then discharged to the atmosphere. Once all additional air is discharged the control float will close the small orifice and restore the sewage effluent to the normal operating level


RGX2-Operation 4

Upon pump stop, Sewage/effluent drains from the sewage air valve, and the negative differential created by the draining liquid causes atmospheric air to push the "Anti-Surge" Float down, opening the Large Orifice and allowing air to displace the draining liquid to prevent potential damaging internal negative pressure.

Selection & Positioning


Technical Specifications


Vent-O-Mat- RGXII - Tech Data1

Type: Double Orifice (Small & Large Orifice) with Bias mechanism for large volume air intake and controlled air discharge.

Size & End Connection:

50mm - Female Threaded BSPT

80-200mm - Flanged AS4087 - PN16

Operating Temperature:

4.4 °C - 80 °C

Model Number / Operating Pressure Range

RGX II 1041 - up to 10 bar

RGX II 1641 - up to 16 bar

Overall Dimensions & Weights


Vent-O-Mat - RGXII - Air Release Valves

For raw sewage pipeline applications. Universal float and seal assembly for easy of removal and maintenance.

Product Code Size Pressure Rating Description
RGXII 050-1641 50mm 16 Bar Anti Surge, Combination ARV - 413mm Height - Threaded Female BSP
RGXII 080-1641 80mm 16 Bar Anti Surge, Combination ARV - 640mm Height - Flanged
RGXII 100-1641 100mm 16 Bar Anti Surge, Combination ARV - 645mm Height - Flanged
RGXII 150-1641 150mm 16 Bar Anti Surge, Combination ARV - 772mm Height - Flanged
RGXII 200-1641 200mm 16 Bar Anti Surge, Combination ARV - 940mm Height - Flanged

For Stainless Steel Material or Higher Pressure Ratings please consult with Deeco.

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