Introduction
If you’ve ever purchased or inspected a ball valve, you’ve probably noticed the marking “WOG” followed by a number like “600” or “1000.” But what does this actually mean?
While it may seem like just another technical code, WOG is a critical pressure rating that determines whether a valve is safe for your system’s media and pressure conditions.
In this article, we’ll explain:
- What WOG stands for and how it’s measured
- What media (water, oil, gas, air, steam) WOG valves are suitable for
- Why WOG ≠ steam-rated
- How WOG compares to similar ratings like WSP and CWP
- What to look for before installing a WOG valve
Whether you’re a maintenance engineer or a DIYer replacing a shutoff valve, this guide will help you avoid common valve selection mistakes and ensure proper use of WOG-rated valves.
1. What Does “WOG” Mean on a Ball Valve?
WOG stands for Water, Oil, Gas, and it refers to the maximum pressure a valve can withstand under non-shock, ambient temperature conditions when used with these types of media.
For example, a valve labeled “600 WOG” means it is rated for 600 PSI working pressure when used with water, oil, or gas—not steam, chemicals, or high-temperature media.
The WOG rating is especially common on brass or stainless steel ball valves, which are used in residential, commercial, and light industrial systems.
2. What Does the WOG Rating Actually Measure?
Many people assume that the “WOG” number printed on a valve is a universal pressure rating—but that’s only partially true.
In reality, the WOG rating measures the valve’s ability to withstand a certain working pressure (in PSI) without failure when used with water, oil, or gas, at ambient temperature, and without shock loads.
What Is “Working Pressure”?
- Working pressure is the continuous pressure a valve can safely operate under in normal service conditions.
- The rating does not account for pressure surges, water hammer, or elevated temperatures.
- Most WOG ratings are determined at 73°F (23°C)—which is considered “ambient” temperature in industrial testing.
For example: A 600 WOG valve can handle 600 PSI of water pressure at room temperature, but it may not hold the same pressure at 200°F or in a gas system.
What WOG Does NOT Cover
WOG does not account for:
- Steam applications (that’s WSP)
- High temperatures (beyond rated limits of seals or body)
- Corrosive fluids or aggressive chemicals
- Food-grade or sanitary applications
- Burst pressure (which is usually several times higher than WOG)
Based on Industry Standards
WOG ratings are typically defined or tested in accordance with:
- ASME B16.34 (Valve design standards)
- MSS SP-110 (Ball valve specs for socket/threaded ends)
- API 598 (Pressure test standard for valves)
Reputable manufacturers follow these standards to ensure that the valve marking is not just marketing—it’s certified capacity.
Summary
✅ WOG = maximum non-shock working pressure at ambient temp
❌ WOG ≠ burst pressure, high-temperature pressure, or steam pressure
⚠️ Always match both pressure and temperature when selecting valves
3. What Media and Systems Are WOG Valves Suitable For?
Just because a valve is labeled with a “WOG” rating doesn’t mean it’s appropriate for every fluid or system. WOG-rated valves are designed to work under specific conditions—and using them outside of those conditions can lead to failure, leaks, or worse.
Let’s explore where WOG valves can and cannot be used.
✅ Suitable Systems and Media
WOG-rated valves are typically safe for use in the following systems:
- Cold or ambient temperature water lines
e.g., potable water shutoff, irrigation, general plumbing - Non-corrosive oil systems
e.g., hydraulic circuits with mineral or light lubricating oils - Low- to medium-pressure compressed air lines
e.g., shop air systems (if valve is air-rated) - Fuel delivery lines (non-corrosive fuels)
e.g., diesel, kerosene (check seal compatibility)
These systems are within the normal PSI and temperature limits expected under WOG testing conditions.
Conditional Use (Check Specs First)
Some systems might work with WOG valves, but only if you confirm the manufacturer’s specifications:
- Hot water lines (above 120–140°F)
→ Check seat and seal materials for thermal resistance - Compressed air
→ Confirm if valve has been leak-tested for gases (bubble-tight) - Mild chemical fluids
→ Check chemical compatibility with valve body/seal materials
Not Recommended for WOG Valves
Avoid using WOG-only valves in the following systems:
- Steam lines or boilers
→ Requires WSP rating; WOG valves are not high-temp rated - Superheated fluids or aggressive chemicals
→ Risk of thermal expansion, seal failure, or corrosion - Food-grade or sanitary processing
→ WOG valves are not certified for NSF/ANSI or FDA use - Vacuum or high-pressure gas systems
→ Needs specific testing beyond WOG
Table: WOG Valve Compatibility by System
| Media / System | Safe to Use? | Notes |
|---|---|---|
| Cold Potable Water | ✅ | Standard use case |
| Lubricating / Hydraulic Oil | ✅ | Ensure media is non-corrosive |
| Compressed Air | ⚠️ | Confirm gas-tight rating (not all WOG valves qualify) |
| Hot Water (>140°F) | ⚠️ | Check seal material for temperature tolerance |
| Steam / Boiler Line | ❌ | Requires WSP-rated valve |
| Food-Grade Fluids | ❌ | Requires sanitary certification (NSF/FDA) |
Summary
Use WOG valves when:
- Your media is liquid-based and non-corrosive
- Your temperature stays close to ambient
- The pressure doesn’t exceed the rating
Don’t use them for:
- Steam
- High-temperature systems
- Aggressive chemicals
- Sanitary or medical processing
4. How WOG Compares to WSP and CWP Ratings
If you’re shopping for valves, chances are you’ve seen terms like WOG, WSP, and CWP. While they may look similar on a valve body or spec sheet, each refers to a different type of pressure rating—and using them interchangeably can lead to serious system failures.
Let’s break them down.
WOG – Water, Oil, Gas
- Stands for Water, Oil, Gas
- Indicates non-shock working pressure at ambient temperature (~73°F or 23°C)
- Commonly used in residential and light commercial systems
- Examples: water shutoff, compressed air (if rated), low-temp oil
WSP – Working Steam Pressure
- Stands for Working Steam Pressure
- Indicates the maximum working pressure for saturated steam
- Rated at higher temperatures, typically ≥250°F (121°C)
- Requires specialized valve design, materials, and thermal testing
- Used in boilers, autoclaves, and other high-temp systems
If a valve doesn’t have a WSP marking, don’t use it for steam—even if it has a high WOG rating.
CWP – Cold Working Pressure
- Stands for Cold Working Pressure
- Similar to WOG in meaning but more common in flanged or mechanical specs
- Refers to non-shock pressure at room temperature
- Often used in HVAC, mechanical, or industrial process systems
Table: WOG vs WSP vs CWP Comparison
| Rating | Full Name | Media Type | Temp Range | Use Case Examples |
|---|---|---|---|---|
| WOG | Water, Oil, Gas | Non-corrosive fluids & gas | ~73°F (23°C) | Plumbing, irrigation, air shutoffs |
| WSP | Working Steam Pressure | Steam | ≥250°F (121°C) | Boilers, sterilizers, heating coils |
| CWP | Cold Working Pressure | Water, gas (non-shock) | ~73°F (23°C) | HVAC, mechanical lines |
Summary
- WOG: General-purpose rating for cold water, oil, gas
- WSP: Required for any steam use (even low-pressure steam)
- CWP: Similar to WOG, often used in mechanical specs
Always choose the right rating for your system’s pressure, temperature, and media. Overlooking this can lead to leaks, pressure blowouts, or even catastrophic failure.
5. Why You Should Not Use WOG Valves for Steam
One of the most common and dangerous mistakes made in valve selection is assuming that a WOG-rated valve can handle steam—especially if the pressure rating looks high (e.g., 600 or 1000 PSI).
But WOG ≠ steam-rated, and using the wrong valve in a high-temperature steam system can cause serious failure.
Why Steam Is a Special Case
Unlike cold water or oil, steam is a high-energy fluid with:
- High temperature (usually ≥250°F or 121°C)
- Expanding gas properties
- Thermal cycling (heating and cooling repeatedly)
- Increased risk of seal failure, seat deformation, and body stress
These factors mean that only WSP-rated valves—designed and tested for steam—should be used in such environments.
Risks of Using WOG Valves for Steam
If you install a WOG-only valve in a steam line:
- Soft PTFE seals may melt or lose integrity
- Seats may deform, causing internal leaks
- The valve may fail under pressure, releasing hot vapor suddenly
- It can void warranties, violate safety codes, or risk personal injury
Example: A 600 WOG valve without WSP rating should never be used on a boiler blowdown line or sterilization unit.
What to Look For Instead
- Check for WSP rating in product specs or stamped on the valve
- Make sure the temperature rating meets or exceeds your system requirements
- Use metal-seated or steam-rated soft-seated valves as required
Visual Reminder
Summary
❌ Never assume a high WOG number = steam safety
✅ Always verify WSP rating for any steam or high-temp application
For steam systems, choose valves tested for both pressure and heat
6. FAQs: Understanding WOG Valve Ratings
To help clarify the most common concerns and confusions, here are real-world questions people ask about WOG valves—along with clear, accurate answers.
Is WOG the same as PSI?
Not exactly.
WOG includes a PSI number (e.g., 600 WOG = 600 PSI), but it only applies to non-shock working pressure at ambient temperature for water, oil, or gas.
Can I use a WOG valve for steam?
No.
Steam systems require WSP-rated valves. WOG valves are not designed or tested for high-temperature vapor and may fail under steam pressure.
Can I use a WOG valve for compressed air?
Sometimes.
Some WOG valves are compatible with low-pressure air—but not all are gas-tight. You must verify that the valve has been tested for bubble-tight shutoff in gas applications.
Can WOG valves handle hot water?
Possibly.
Some WOG valves can tolerate hot water up to 180–200°F, but you must check the temperature rating of the seats, seals, and body material. WOG does not guarantee thermal resistance.
Is WOG the same as CWP?
They are functionally similar:
- Both refer to cold, non-shock pressure ratings
- WOG is more common in plumbing and general supply
- CWP is often used in HVAC or mechanical engineering specs
Why is WOG not enough for food-grade systems?
WOG valves are not certified under NSF/ANSI or FDA standards.
If your application involves potable water processing or food handling, use valves that are specifically sanitary-rated.
What happens if I exceed the WOG rating?
The valve may:
- Leak internally or externally
- Fail under pressure, releasing fluid suddenly
- Deform due to overstressed seals or body
- Cause system downtime or safety hazards
How can I tell if a valve is WSP-rated?
Look for markings like “WSP” on the body, or check the manufacturer’s datasheet.
If it’s not marked for steam, don’t assume it is safe—even if the WOG pressure rating is high.
Summary
WOG is a helpful baseline—but it does not cover temperature, steam, or special applications.
When in doubt, always consult the valve datasheet, pressure-temperature chart, and relevant certifications.
7. Conclusion: What WOG Really Means—and What It Doesn’t
Understanding the WOG rating is essential when selecting a ball valve. It tells you how much pressure the valve can safely handle under specific conditions—but only for certain types of media and only at certain temperatures.
Here’s what you should remember:
- WOG = Water, Oil, Gas, rated for non-shock pressure at ambient temperature
- The number (e.g., 600 WOG) indicates PSI working pressure, not burst strength or temperature resistance
- WOG-rated valves are generally not suitable for steam, food-grade, or high-temp use
- WSP and CWP ratings cover steam and mechanical system conditions respectively—and are not interchangeable with WOG
- Always match your valve to your system’s media, temperature, and pressure requirements
Quick Selection Checklist
| Scenario | Use WOG Valve? | Notes |
|---|---|---|
| Cold water shutoff | ✅ | Ideal application |
| Lubricating oil line | ✅ | Non-corrosive only |
| Compressed air system | ⚠️ | Confirm leak-tight rating |
| Steam boiler line | ❌ | Requires WSP-rated valve |
| Hot water (180°F or more) | ⚠️ | Check thermal limits of valve seals and body |
| Food or sanitary processing line | ❌ | Requires NSF or FDA certification |
Need Help Choosing the Right Valve?
At XHVAL, we offer a wide range of high-quality ball valves for every pressure class—from WOG-rated shutoff valves to WSP-rated steam valves and CWP-rated industrial solutions.
→ Browse Our Ball Valve Pressure Ratings
→ Contact XHVAL for Expert Valve Selection Support
Get in touch today and make sure your valve matches your system—the right rating makes all the difference.