The Castair PK30 is a 1.5 HP single-stage, single-cylinder bare pump with a 10" (1A-series) flywheel and 8 oz. oil capacity. Like the PK20, this is the pump assembly only — no motor, no tank. The key difference from the PK20 is the larger 10" flywheel, which affects the drive ratio and adds rotational mass for smoother compression strokes. The PK30 is used when the motor pulley and belt drive configuration requires a larger flywheel OD to achieve the correct pump RPM from the available motor speed.
Note: Cast Air did not provide a dedicated manufacturer product page for this pump. Specifications are drawn from the product listing. Call us to confirm CFM output, max PSI rating, and motor/belt compatibility for your specific application before ordering.
PK30 vs. PK20 — Which Do You Need?
Both the PK20 and PK30 are 1.5 HP single-cylinder single-stage pumps with the same oil capacity and identical HP rating. The difference is flywheel size: 7.5" on the PK20, 10" on the PK30. The flywheel OD affects your drive ratio and the required motor pulley size. When replacing an existing pump, you need to match the flywheel OD of the original, not just the HP rating — otherwise the motor pulley will produce the wrong pump RPM. If your original pump had a 10" flywheel, the PK30 is the correct replacement. If it had a 7.5" flywheel, order the PK20.
Why Flywheel Size Matters
The flywheel on a piston compressor pump serves two purposes: it provides the groove surface for the belt drive (setting the driven side of the ratio), and it adds rotational inertia to smooth out the compression stroke. A 10" flywheel on the PK30 paired with a motor pulley of approximately 5.1-6.2" OD (at 1,750 RPM motor speed) achieves the target pump RPM of 900-1,100. If the same motor and motor pulley were connected to the PK20's 7.5" flywheel, the pump would spin much faster — outside its rated RPM range. Match the flywheel to the drive system, not just the horsepower.
Pump Specification Details
- Part Number: PK30
- HP Rating: 1.5 HP
- Stage: Single stage
- Cylinders: 1
- Flywheel OD: 10" (1A-series flywheel)
- Oil Capacity: 8 oz.
- Drive: Belt drive
- Price: $241.01
Oil-Lubricated Pump Maintenance
The PK30 is oil-lubricated with an 8 oz. crankcase. Proper oil maintenance is critical to pump longevity:
- Check oil level before each use — low oil is the most common cause of premature pump failure
- Change oil at Cast Air's specified intervals (confirm interval in the pump documentation)
- Use compressor pump oil — not motor oil, not synthetic automotive oil unless specifically approved by Cast Air
- Watch the oil sight glass or dipstick; overfilling causes oil carry-over into the tank and air lines
When Does a Shop Need the PK30?
- Original 1.5 HP single-cylinder Cast Air pump with 10" flywheel has failed
- Motor and tank are in serviceable condition and pump is the only failed component
- Building a custom 1.5 HP compressor where a 10" flywheel drive configuration is required
- Light to medium shop demand — inflation, blow guns, intermittent pneumatic nail guns or light impact use
Cast Air Bare Pump Comparison
- PK20 — 1.5 HP, 1-cylinder, 7.5" flywheel, 8 oz. — $194.81 — same HP as PK30, smaller flywheel
- PK30 — 1.5 HP, 1-cylinder, 10" flywheel, 8 oz. — $241.01 (this unit) — same HP, larger flywheel for different drive ratio
- PK50 — 2 HP, V-2 cylinder, 10" flywheel, 16 oz. — $371.91 — step up in CFM output and HP
- PK60 — 3.5 HP, V-2 cylinder, 10" flywheel, 32 oz. — $432.74 — heavy shop applications
Technical Specifications
- Part Number: PK30
- Manufacturer: Cast Air (Castair)
- HP: 1.5
- Stage: Single stage
- Cylinders: 1
- Flywheel OD: 10" (1A-series)
- Oil Capacity: 8 oz.
- Drive Type: Belt drive (flywheel included, belt not included)
- Price: $241.01
- CFM/PSI: Not confirmed in listing — call for current performance specs
- Manufacturer Data: Product page not available — specifications from product listing data
What Is Included
- 1x Castair PK30 bare pump with 10" flywheel
Motor, motor pulley, belt, tank, pressure switch, safety valve, and all connecting hardware are not included. This is the pump assembly only.
Why Buy From Air Compressor Factory Direct?
When replacing a pump, matching the flywheel OD to the existing drive configuration is as important as matching the HP. We have been working with Cast Air pump assemblies since 2016 and can help you confirm whether the PK30 (10" flywheel) or PK20 (7.5" flywheel) is the correct replacement for your specific unit. Free shipping, free tech support, full manufacturer warranty.
- Cast Air specialist since 2016
- Free shipping on all orders
- Free tech support — we confirm the correct flywheel and drive configuration
- Full manufacturer warranty
- Honest guidance — we will tell you if PK20 is the right call instead
Call 866-217-0063 for quick answers and help!
