The Castair PA6 is a 3/8" NPT female air fitting, an OEM replacement component for Cast Air compressor systems. The 3/8" NPT size is one of the most commonly used thread sizes on smaller Cast Air compressors and on accessory ports of larger units — gauge connections, unloader line connections, regulator inlets, and auxiliary air ports frequently use 3/8" NPT female threads. If a fitting is damaged or a connection point needs rebuilding, the PA6 restores it to original specification.
Note: Cast Air did not provide a dedicated manufacturer product page for this fitting. The PA6 designation and NPT female specification are drawn from the product listing. Contact us to confirm the exact thread size and application before ordering.
3/8" NPT Female Fittings on Compressors
The 3/8" NPT size sits between the 1/4" small-accessory size and the 1/2" main-line size in typical compressor plumbing. On Cast Air units, 3/8" NPT female ports commonly appear at regulator inlets, small manifold branches, check valve connections, and secondary outlet ports. The NPT taper (3/4" per foot) allows a pressure-tight joint when assembled with thread sealant. Always use PTFE tape or pipe thread compound on NPT joints — finger-tight alone will not hold air pressure reliably.
Fitting Specification Details
- Part Number: PA6
- Thread Type: NPT (National Pipe Taper)
- Thread Gender: Female
- Nominal Size: 3/8" (3/8" NPT female)
- Thread Count: 18 TPI (standard 3/8" NPT)
- Application: Cast Air compressor plumbing — regulator ports, gauge connections, auxiliary air outlets
- Compatibility: Cast Air compressor systems with 3/8" NPT female connection points
Common Applications for the PA6
- Regulator inlet ports — many Cast Air regulators use 3/8" NPT female inlet threads
- Pressure gauge ports — smaller gauge connections on single-cylinder and small two-cylinder units
- Unloader valve fittings — unloader lines on compressor heads frequently use 3/8" NPT
- Check valve connections — tank check valve ports on smaller Cast Air units
- Secondary outlet ports — auxiliary air outlets on multi-port manifolds
When Does a Shop Need the PA6?
- Existing 3/8" NPT female fitting is cross-threaded, corroded, or cracked
- Air is leaking at a 3/8" NPT connection and the fitting is the source (not the sealant)
- Rebuilding a Cast Air compressor assembly that required disassembly of 3/8" NPT connections
- Adding a regulator, gauge, or valve to a Cast Air system that has an open 3/8" NPT port
Technical Specifications
- Part Number: PA6
- Manufacturer: Cast Air (Castair)
- Thread Standard: NPT (National Pipe Taper)
- Thread Gender: Female
- Nominal Size: 3/8" NPT
- Thread Count: 18 TPI (standard 3/8" NPT)
- Manufacturer Data: Product page not available — specifications from product listing data
What Is Included
- 1x Castair PA6 3/8" NPT female fitting
Thread sealant is not included. Use PTFE tape or pipe thread compound rated for compressed air service on all NPT connections.
Why Buy From Air Compressor Factory Direct?
Small fittings make a big difference in plumbing integrity — and OEM Cast Air parts are manufactured to the thread class and material spec of the original. We have been supplying Cast Air compressor parts since 2016. If you are not sure whether PA6 is the correct size for your connection point, call us with the compressor model number and location of the fitting and we will confirm before you order. Free shipping and free tech support on every order.
- Cast Air specialist since 2016
- Free shipping on all orders
- Free tech support — we confirm the right fitting before you order
- Full manufacturer warranty
- OEM parts — correct material and thread class for pressurized air service
Call 866-217-0063 for quick answers and help!
