Relief Valves and Vacuum Breakers
Relief valves and vacuum breakers are vital safety devices that protect systems and equipment from overpressure or vacuum conditions. Relief valves are designed to automatically relieve excessive pressure within a system, preventing potential damage or catastrophic failure. They are commonly used in boilers, pressure vessels, pipelines, and hydraulic systems. On the other hand, vacuum breakers are utilized to prevent the formation of a vacuum or negative pressure within a system, which can lead to implosion or damage. Vacuum breakers are commonly found in plumbing systems, water supply lines, and industrial processes. These valves ensure system integrity and safety by releasing pressure or preventing vacuum, safeguarding equipment, and preventing potential hazards.
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The Apollo 29303A70 is a Relief Valve 3/4" E Ori. Typical applications span industrial processing, commercial mechanical systems, and HVAC environments. Backed by Apollo's commitment to quality, the 29303A70 is built to perform under real-world conditions. It is designed to comply with applicable UL and NSF requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303A75 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across plumbing, fire protection, and industrial processing sectors. Apollo products are trusted by engineers and specifiers worldwide. This product meets relevant UL and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303A75S is a Relief Valve 3/4" E Ori. It is commonly found in industrial processing, plumbing, and HVAC applications. The 29303A75S reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant UL and FM standards.
$682.23$807.75
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303A80 is a Relief Valve 3/4" E Ori. Typical applications span plumbing, HVAC, and fire protection environments. Apollo products are trusted by engineers and specifiers worldwide.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303A80S is a Relief Valve 3/4" E Ori. This product serves professionals across HVAC, commercial mechanical systems, and oil and gas sectors. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable ASME and NSF requirements.
$682.23$807.75
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303A85 is a Relief Valve 3/4" E Ori. It is commonly found in HVAC, industrial processing, and oil and gas applications. The 29303A85 reflects Apollo's long-standing reputation for quality and innovation. It is designed to comply with applicable ASME and NSF requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303A85S from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in fire protection, marine, and commercial mechanical systems applications. The 29303A85S reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant UL and FM standards.
$682.23$807.75
Available for Purchase
Subject to factory lead times
Part number 29303A90 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across HVAC, industrial processing, and marine sectors. As a leader in valves and flow control, Apollo manufactures every component to exacting standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303A95 is a Relief Valve 3/4" E Ori. Typical applications span plumbing, fire protection, and marine environments. The 29303A95 reflects Apollo's long-standing reputation for quality and innovation.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303K100 is a Relief Valve 3/4" E Ori. Typical applications span HVAC, oil and gas, and marine environments. Apollo Valves is recognized globally for engineering products that meet strict performance standards. This product meets relevant NSF and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303K125 from Apollo is a Relief Valve 3/4" E Ori. Typical applications span plumbing, industrial processing, and fire protection environments. As a leader in valves and flow control, Apollo manufactures every component to exacting standards. This product meets relevant NSF and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303K125S is a Relief Valve 3/4" E Ori. Typical applications span HVAC, oil and gas, and commercial mechanical systems environments. As a leader in valves and flow control, Apollo manufactures every component to exacting standards. It is designed to comply with applicable NSF and ASME requirements.
$682.23$807.75
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303K135 is a Relief Valve 3/4" E Ori. Typical applications span commercial mechanical systems, industrial processing, and HVAC environments. The 29303K135 reflects Apollo's long-standing reputation for quality and innovation. It is designed to comply with applicable ASME and UL requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303K150 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across plumbing, fire protection, and industrial processing sectors. The 29303K150 reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant FM and ASME standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303K175 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across industrial processing, plumbing, and HVAC sectors. Apollo products are trusted by engineers and specifiers worldwide.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303K175Q from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across commercial mechanical systems, fire protection, and marine sectors. Apollo Valves is recognized globally for engineering products that meet strict performance standards. It is designed to comply with applicable NSF and ASME requirements.
$578.75$685.24
Available for Purchase
Subject to factory lead times
The 29303K200 from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in plumbing, oil and gas, and fire protection applications. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable NSF and UL requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303L100 is a Relief Valve 3/4" E Ori. It is commonly found in plumbing, industrial processing, and oil and gas applications. The 29303L100 reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant ASME and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303L120 is a Relief Valve 3/4" E Ori. Typical applications span oil and gas, HVAC, and plumbing environments. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable ASME and UL requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303L125 from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in commercial mechanical systems, industrial processing, and marine applications. Backed by Apollo's commitment to quality, the 29303L125 is built to perform under real-world conditions.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303L135 from Apollo is a Relief Valve 3/4" E Ori. Typical applications span commercial mechanical systems, fire protection, and oil and gas environments. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable NSF and FM requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303L140 from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in fire protection, marine, and plumbing applications. Apollo products are trusted by engineers and specifiers worldwide. This product meets relevant NSF and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303L150 is a Relief Valve 3/4" E Ori. This product serves professionals across HVAC, plumbing, and oil and gas sectors. Backed by Apollo's commitment to quality, the 29303L150 is built to perform under real-world conditions. It is designed to comply with applicable FM and ASME requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303L200 is a Relief Valve 3/4" E Ori. It is commonly found in HVAC, fire protection, and oil and gas applications. The 29303L200 reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant NSF and UL standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo 29303A70 is a Relief Valve 3/4" E Ori. Typical applications span industrial processing, commercial mechanical systems, and HVAC environments. Backed by Apollo's commitment to quality, the 29303A70 is built to perform under real-world conditions. It is designed to comply with applicable UL and NSF requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303A75 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across plumbing, fire protection, and industrial processing sectors. Apollo products are trusted by engineers and specifiers worldwide. This product meets relevant UL and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303A75S is a Relief Valve 3/4" E Ori. It is commonly found in industrial processing, plumbing, and HVAC applications. The 29303A75S reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant UL and FM standards.
$682.23$807.75
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303A80 is a Relief Valve 3/4" E Ori. Typical applications span plumbing, HVAC, and fire protection environments. Apollo products are trusted by engineers and specifiers worldwide.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303A80S is a Relief Valve 3/4" E Ori. This product serves professionals across HVAC, commercial mechanical systems, and oil and gas sectors. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable ASME and NSF requirements.
$682.23$807.75
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303A85 is a Relief Valve 3/4" E Ori. It is commonly found in HVAC, industrial processing, and oil and gas applications. The 29303A85 reflects Apollo's long-standing reputation for quality and innovation. It is designed to comply with applicable ASME and NSF requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303A85S from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in fire protection, marine, and commercial mechanical systems applications. The 29303A85S reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant UL and FM standards.
$682.23$807.75
Available for Purchase
Subject to factory lead times
Part number 29303A90 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across HVAC, industrial processing, and marine sectors. As a leader in valves and flow control, Apollo manufactures every component to exacting standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303A95 is a Relief Valve 3/4" E Ori. Typical applications span plumbing, fire protection, and marine environments. The 29303A95 reflects Apollo's long-standing reputation for quality and innovation.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303K100 is a Relief Valve 3/4" E Ori. Typical applications span HVAC, oil and gas, and marine environments. Apollo Valves is recognized globally for engineering products that meet strict performance standards. This product meets relevant NSF and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303K125 from Apollo is a Relief Valve 3/4" E Ori. Typical applications span plumbing, industrial processing, and fire protection environments. As a leader in valves and flow control, Apollo manufactures every component to exacting standards. This product meets relevant NSF and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303K125S is a Relief Valve 3/4" E Ori. Typical applications span HVAC, oil and gas, and commercial mechanical systems environments. As a leader in valves and flow control, Apollo manufactures every component to exacting standards. It is designed to comply with applicable NSF and ASME requirements.
$682.23$807.75
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303K135 is a Relief Valve 3/4" E Ori. Typical applications span commercial mechanical systems, industrial processing, and HVAC environments. The 29303K135 reflects Apollo's long-standing reputation for quality and innovation. It is designed to comply with applicable ASME and UL requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303K150 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across plumbing, fire protection, and industrial processing sectors. The 29303K150 reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant FM and ASME standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303K175 from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across industrial processing, plumbing, and HVAC sectors. Apollo products are trusted by engineers and specifiers worldwide.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303K175Q from Apollo is a Relief Valve 3/4" E Ori. This product serves professionals across commercial mechanical systems, fire protection, and marine sectors. Apollo Valves is recognized globally for engineering products that meet strict performance standards. It is designed to comply with applicable NSF and ASME requirements.
$578.75$685.24
Available for Purchase
Subject to factory lead times
The 29303K200 from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in plumbing, oil and gas, and fire protection applications. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable NSF and UL requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303L100 is a Relief Valve 3/4" E Ori. It is commonly found in plumbing, industrial processing, and oil and gas applications. The 29303L100 reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant ASME and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Engineered by Apollo, the 29303L120 is a Relief Valve 3/4" E Ori. Typical applications span oil and gas, HVAC, and plumbing environments. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable ASME and UL requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303L125 from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in commercial mechanical systems, industrial processing, and marine applications. Backed by Apollo's commitment to quality, the 29303L125 is built to perform under real-world conditions.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The 29303L135 from Apollo is a Relief Valve 3/4" E Ori. Typical applications span commercial mechanical systems, fire protection, and oil and gas environments. Apollo products are trusted by engineers and specifiers worldwide. It is designed to comply with applicable NSF and FM requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
Part number 29303L140 from Apollo is a Relief Valve 3/4" E Ori. It is commonly found in fire protection, marine, and plumbing applications. Apollo products are trusted by engineers and specifiers worldwide. This product meets relevant NSF and FM standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303L150 is a Relief Valve 3/4" E Ori. This product serves professionals across HVAC, plumbing, and oil and gas sectors. Backed by Apollo's commitment to quality, the 29303L150 is built to perform under real-world conditions. It is designed to comply with applicable FM and ASME requirements.
$529.54$626.97
Available for Purchase
Subject to factory lead times
The Apollo Valves 29303L200 is a Relief Valve 3/4" E Ori. It is commonly found in HVAC, fire protection, and oil and gas applications. The 29303L200 reflects Apollo's long-standing reputation for quality and innovation. This product meets relevant NSF and UL standards.
$529.54$626.97
Available for Purchase
Subject to factory lead times
FAQS
- A relief valve (also called a safety relief valve or pressure relief valve) is a self-actuated valve that automatically opens to release fluid when the system pressure exceeds a preset limit, protecting pressure vessels, boilers, piping systems, and other pressurized equipment from dangerous overpressure conditions that could cause catastrophic failure, equipment damage, or injury to personnel. When system pressure rises to the valve's set pressure, the force of the pressure acting on the valve's disc or poppet overcomes the spring force holding it closed, and the valve opens to vent fluid (steam, air, gas, or liquid) until the pressure drops back to a safe level. Relief valves are required by ASME Boiler and Pressure Vessel Code, OSHA regulations, insurance requirements, and local building codes on virtually all pressurized equipment. Centro carries Apollo ASME Section I and Section VIII certified safety relief valves in bronze construction with brass or stainless steel trim, available with PFA and metal seat styles, in sizes from 1/2 inch to 2-1/2 inches, with set pressures from 5 to 300 PSIG.
- A vacuum breaker is a valve that automatically opens to admit air into a piping system when the internal pressure drops below atmospheric pressure (a vacuum condition). Vacuum conditions in piping systems can cause several problems: collapse of thin-walled tanks, vessels, or piping that are not designed to withstand external (atmospheric) pressure; back-siphonage of contaminated fluid into potable water supply systems; damage to pumps, heat exchangers, and other equipment when vacuum causes cavitation or implosion; and inability to drain tanks or vessels that become vacuum-locked. Vacuum breakers are installed at high points in piping systems, on tanks and vessels, and on water supply lines upstream of equipment that could create a back-siphon condition. When the internal pressure drops below atmospheric pressure, the vacuum breaker opens and allows air to enter the system, breaking the vacuum and preventing the problems listed above. When pressure returns to normal (positive), the vacuum breaker closes to prevent air from continuing to enter and to prevent fluid from leaking out.
- While the terms are often used interchangeably in general conversation, there are technical differences defined by ASME codes. A safety valve is designed for compressible fluid service (steam, air, gases) and opens rapidly (pops) to full lift when the set pressure is reached. The rapid opening characteristic is necessary because compressible fluids expand enormously in volume when pressure is released, so the valve must open fully and quickly to handle the large volume of gas discharge needed to relieve the overpressure. A relief valve is designed for incompressible fluid service (liquids) and opens gradually in proportion to the overpressure above the set point. Liquids do not expand significantly when released, so a gradual opening is sufficient and desirable to avoid system instability. A safety relief valve combines both characteristics — it can function as a safety valve on compressible fluids (popping open) or as a relief valve on liquids (opening proportionally). The Apollo ASME-certified valves available through Centro are suitable for steam, air, and non-hazardous gas service and carry both Section I (steam boilers) and Section VIII (pressure vessels) capacity certifications.
- ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code requires that relief valves protecting certain equipment must be capacity certified and stamped to indicate compliance. ASME Section I covers steam power boilers — any relief valve protecting a steam boiler must carry the ASME Section I stamp (V stamp) and must have been capacity tested by an ASME-authorized laboratory. ASME Section VIII covers unfired pressure vessels — relief valves protecting process vessels, air receivers, heat exchangers, and similar equipment must carry the ASME Section VIII stamp (UV stamp). These certifications verify that the relief valve has been tested and proven to relieve the rated capacity at its set pressure, ensuring it can adequately protect the equipment. The Apollo safety relief valves available through Centro carry both ASME Section I and Section VIII certified capacities, with set pressures from 5 to 300 PSIG at temperatures from -60°F to 406°F, making them suitable for steam boilers, pressure vessels, piping systems, and similar equipment.
- Selecting a relief valve requires matching several parameters. Set pressure must be at or below the maximum allowable working pressure (MAWP) of the equipment being protected — the valve must open before the equipment reaches its pressure limit. Relieving capacity must be sufficient to handle the worst-case overpressure scenario (such as a failed-open regulator, fire exposure, or thermal expansion). Connection size and type must match the piping. Body and trim materials must be compatible with the process fluid and temperature. The seat material (PFA or metal) depends on the service — PFA provides tighter shutoff at lower pressures while metal seats handle higher temperatures and more aggressive media. For maintenance, relief valves should be tested and recertified on a regular schedule (typically annually for critical applications) to verify they open at the correct set pressure and reseal properly. Look for signs of leakage, corrosion, or buildup on the seat and disc surfaces. Never paint, plug, or obstruct the discharge opening. Never exceed the nameplate set pressure. Keep records of all testing, maintenance, and replacement for compliance with ASME, OSHA, and insurance requirements.