Cast Air NT25 — 1/4" Nylon Tubing for Air Compressor Control Circuits
This is 1/4" nylon tubing, sold by the foot, designed for use in pneumatic control circuits on air compressors. If you are replacing or extending the tubing that runs between your pressure switch, pilot valve, unloader valve, or any other control-circuit component, this is the material you need. It is flexible enough to route through tight spaces, rated for the pressures and temperatures found in compressor control lines, and compatible with standard 1/4" compression fittings and push-to-connect fittings used throughout the industry.
Nylon tubing is the standard choice for signal lines and sensing lines on reciprocating compressors. It is not used for main air discharge lines — that is what copper tubing is for. But for the low-flow, low-volume lines that carry pilot signals from your pressure switch to your unloader, or from your regulator to a downstream control, nylon is the correct material: lightweight, flexible, easy to cut and route, and resistant to kinking when installed with reasonable bend radii.
What This Tubing Is Used For
- Pressure switch sensing lines: The small-bore line that carries tank pressure to the pressure switch diaphragm. When this line cracks or hardens, the switch reads incorrectly or fails to cycle.
- Pilot valve signal lines: On two-stage compressors with pneumatic unloaders, a pilot signal line carries regulated pressure to the unloader pilot valve. This is one of the most common lines to replace during a service call.
- Unloader lines: The line between the pilot valve and the unloader valve itself. Subject to cycling pressure every time the compressor starts and stops.
- Regulator outlet lines: When a secondary regulator feeds a downstream tool or manifold, 1/4" nylon tubing is a clean, flexible connection method.
- Any low-flow control circuit: Anywhere on the compressor where you need to carry a pressure signal, not a main airflow stream.
Material Properties
- Material: Nylon (polyamide)
- Outside diameter: 1/4" — fits standard 1/4" OD compression and push-to-connect fittings
- Flexibility: Flexible and easy to route; holds shape without kinking when bent with reasonable radius
- Temperature rating: Suitable for the temperature ranges found in compressor control circuit environments
- Pressure rating: Appropriate for compressor control line pressures (signal lines, not main discharge)
- Color: Natural nylon (semi-transparent or white)
- Cut-to-length: Sold by the foot; specify feet required when ordering
Nylon Tubing vs. Copper Tubing — Which Do You Need?
Cast Air offers both nylon and copper tubing. Here is a straightforward guide:
- Use nylon (NT25) for: Control signal lines, sensing lines, pilot lines, unloader signal lines — anywhere flexibility is more important than heat resistance, and where the line does not carry high-volume discharge air
- Use 1/4" copper (CT25) for: Discharge lines or control circuits where a more rigid, heat-tolerant line is needed — copper handles heat from compressed air better in high-cycle applications
- Use 1/2" copper (CT50) for: Larger discharge or inter-stage lines on two-stage compressors
- Use 5/8" copper (CT58) for: Larger compressor discharge connections
- Use 3/4" copper (CT75) for: High-volume main lines where copper is specified
If you are replacing a line and are not sure whether the original was nylon or copper, look at the existing installation. Nylon lines are typically flexible and routed with gradual bends. Copper lines are rigid and will have visible bends formed with a tubing bender.
Ordering Notes
- Sold by the foot: Specify the number of feet required when placing your order
- Price: $3.85 per foot
- Minimum order: Contact us for minimum quantity if ordering a single foot
- Fittings: Not included — order the appropriate 1/4" compression or push-to-connect fittings separately if needed
Common Replacement Scenarios
- Compressor short-cycling: A cracked or blocked sensing line can cause the pressure switch to read erratic pressures, resulting in short-cycling or failure to cut out. Replacing the sensing line is often the first step in diagnosing this symptom.
- Unloader not releasing on restart: A damaged pilot signal line can prevent the unloader from getting the signal it needs to open on startup. A new section of nylon tubing costs less than four dollars per foot and is the correct place to start diagnosis.
- Scheduled preventive maintenance: On compressors that run high cycle counts, replacing nylon control lines every few years is inexpensive insurance against unexpected failures during peak demand.
- System modification or extension: If you are adding a secondary pressure switch, installing an additional regulator station, or reconfiguring a control panel, NT25 tubing lets you route new signal lines cleanly and professionally.
Technical Specifications
- Part Number: NT25
- Outside Diameter: 1/4"
- Material: Nylon
- Sold: By the foot
- Price: $3.85 per foot
- Application: Pneumatic control circuits — signal lines, sensing lines, unloader lines, pilot valve lines
- Compatible fittings: Standard 1/4" OD compression fittings and push-to-connect fittings
Why Buy From Air Compressor Factory Direct?
We have been supplying air compressor parts and replacement components since 2016. We stock Cast Air OEM parts because they are the correct specification for the machines they came off of. When you order NT25 tubing here, you are getting the same material Cast Air uses at the factory — not a generic substitute that might differ in wall thickness or pressure rating.
- Free shipping on qualifying orders
- Free tech support: Call 866-217-0063 and talk to someone who knows compressors
- Full manufacturer warranty on all parts
- Honest guidance: If you are not sure whether you need nylon or copper tubing, or how much to order, call us and we will help you figure it out before you place the order — not after
Call 866-217-0063 for quick answers and help!
