Running a single air compressor can limit your airflow capacity—especially during high-demand tasks like sandblasting, automotive painting, or powering multiple pneumatic tools simultaneously. If you’ve ever wondered how to plumb two air compressors together with check valves, you’re not alone. Many DIYers and professionals seek this setup to boost CFM (cubic feet per minute), ensure system redundancy, or simply future-proof their workshop. In this guide, we’ll walk you through a safe, efficient, and code-compliant method to connect two compressors using check valves—so you get reliable air power without backflow or pressure conflicts.
Why Use Check Valves When Plumbing Two Air Compressors?
Before diving into the “how,” it’s essential to understand the “why.”
When you connect two compressors directly to a shared air line without check valves, pressurized air from one unit can flow backward into the other—especially if one compressor is off or at a lower pressure. This backflow can:
Cause unnecessary wear on the idle compressor’s pump
Trigger false pressure readings
Waste energy and reduce system efficiency
Potentially damage internal components over time
A check valve (also called a non-return valve) allows air to flow in only one direction—out of the compressor and into the main line—while preventing reverse flow. As noted by the Compressed Air & Gas Institute (CAGI), proper valve placement is critical for system longevity and safety.
💡 Pro Tip: Always install a check valve immediately after each compressor’s discharge port—before any shared piping begins.
What You’ll Need: Tools & Materials
Here’s a complete checklist before you start:
Item
Purpose
Two air compressors
Ensure they’re compatible in voltage and duty cycle
Two inline check valves (rated for your system’s PSI)
Prevent backflow between units
Air receiver tank (optional but recommended)
Stabilizes pressure and reduces cycling
Galvanized steel or aluminum piping (½”–¾” diameter)
⚠️ Safety First: Always disconnect power and fully depressurize both compressors before working on the system.
Closeup of Mechanic Hooking Up a Pipe on Stationary Wheel Air Compressor Tool Installed in Professional Car Workshop.
Step-by-Step Guide: How to Plumb Two Air Compressors Together with Check Valves
Follow these steps carefully to create a balanced, efficient dual-compressor system:
Step 1: Position Your Compressors
Place both compressors on a stable, level surface with adequate ventilation. Allow at least 18 inches of clearance around each unit for airflow and maintenance access.
Step 2: Install Individual Check Valves
Attach a check valve directly to the discharge port of each compressor.
Ensure the arrow on the valve body points away from the compressor (toward the main line).
Use PTFE tape on all threaded connections to prevent leaks.
Step 3: Add Isolation Ball Valves (Optional but Smart)
Install a ball valve just after each check valve. This lets you shut off one compressor for service without draining the entire system.
Step 4: Connect to a Common Header
Run piping from each check valve to a common header pipe (the main air line that feeds your tools).
Use T-fittings or a manifold block to merge the lines cleanly.
Keep pipe runs as short and straight as possible to minimize pressure drop.
Step 5: Integrate an Air Receiver Tank (Highly Recommended)
Connect the common header to a central air receiver tank (e.g., 60–80 gallons).
The tank acts as a buffer, smoothing out pressure spikes and reducing compressor cycling.
According to the U.S. Department of Energy, adding storage can improve system efficiency by up to 20%.
Step 6: Test for Leaks and Balance
Pressurize the system gradually.
Spray soapy water on all joints—if bubbles form, tighten or reseal.
Monitor both compressors’ pressure gauges. They should build pressure independently and shut off at their set points without affecting each other.
Skipping check valves → leads to backfeeding and motor strain.
Using undersized piping → causes excessive pressure drop (aim for ≤2 PSI loss across the system).
Ignoring pressure settings → both compressors should have similar cut-in/cut-out pressures (e.g., 90–120 PSI).
Placing filters or dryers before check valves → can trap moisture and cause corrosion upstream.
Benefits of a Dual Compressor Setup with Check Valves
Benefit
Explanation
Increased CFM
Run high-demand tools without stalling.
System Redundancy
If one compressor fails, the other keeps working.
Reduced Wear
Less frequent cycling extends motor life.
Scalability
Easy to add a third compressor later.
A real-world example: A California auto body shop increased productivity by 35% after switching from one 5 HP compressor to two 3 HP units plumbed with check valves—allowing simultaneous use of spray guns and impact wrenches.
FAQ Section
Q1: Can I run two different-sized compressors together?
Yes, but it’s best if they operate within the same pressure range. A small 2-gallon pancake compressor paired with a 60-gallon industrial unit may cause imbalance. Match duty cycles and PSI ratings when possible.
Q2: Do I need a separate pressure switch for each compressor?
Absolutely. Each compressor must control its own on/off cycle based on system pressure. Never wire them to a single switch unless using a master controller designed for multi-compressor setups.
Q3: Will this setup double my airflow (CFM)?
Not exactly. Total CFM is additive only if both compressors are running simultaneously. However, due to piping losses and timing differences, expect ~90–95% of theoretical combined output.
Q4: Where should I install the air dryer or filter?
Place filtration after the common header or receiver tank—not between the compressor and check valve. This ensures clean, dry air reaches all tools without interfering with check valve operation.
Q5: Can I use flexible hoses instead of rigid piping?
You can, but rigid piping (aluminum or steel) is preferred for permanent setups. Hoses introduce more friction loss and are prone to kinking or leaks over time.
Q6: How often should I maintain the check valves?
Inspect check valves every 6 months for debris or sticking. Replace if you notice air leaking backward or inconsistent pressure behavior.
Conclusion
Learning how to plumb two air compressors together with check valves is a smart investment for any serious workshop, garage, or small business. Not only does it boost your available airflow, but it also adds reliability and flexibility to your compressed air system. By following the steps above—and avoiding common pitfalls—you’ll create a setup that’s efficient, safe, and built to last.
If this guide helped you, share it with a fellow DIYer or technician on Facebook, Reddit (r/Tools or r/Workshop), or your favorite forum! Got questions? Drop them in the comments—we’re happy to help you build a better air system.
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