The Castair DD20 is a 1.5 HP single-stage, single-cylinder cast iron air compressor pump sold as a bare pump unit with the motor already mounted — but no flywheel. At 45 pounds, it's the lightest motor-mounted bare pump in the Castair lineup, sized for compressor builds where you already have or are sourcing a flywheel and tank separately. This is a component sale, not a complete compressor. It's what you buy when you're rebuilding an existing machine, building a custom unit from scratch, or replacing a failed pump-and-motor assembly on a smaller portable or stationary compressor.
What You're Getting — And What You're Not
The DD20 comes with the pump and motor assembled together — the motor is already mounted to the pump crankcase. This saves you from having to source a compatible motor separately and figure out shaft sizing and frame matching. What it does not include is a flywheel. If you're replacing a pump in an existing compressor, you may be able to reuse the original flywheel. If you're building new, you'll need to source a flywheel that fits the pump's 1-inch keyed crankshaft (verify shaft specs before ordering).
This is also a bare pump — no tank, no pressure switch, no safety valve, no gauges, no air filter. All of those are separate. For a complete compressor build or rebuild using the DD20, you'll also need to source those components, either individually from Castair's accessories and major components catalog or from your existing compressor if you're doing a pump swap.
Pump Specifications
- Model: DD20
- Horsepower: 1.5 HP
- Stage: Single-stage
- Cylinder configuration: 1 cylinder
- Flywheel: None included (flywheel sold separately)
- Oil capacity: 8 oz.
- Weight: 45 lbs (pump with motor, no flywheel)
- Warranty: 1 year parts only when properly installed and maintained
How DD20 Fits the Castair Pump Lineup
Castair's cast iron bare pump lineup covers a wide range of HP from 1.5 HP single-cylinder units up to 15–25 HP two-stage V4 assemblies. Here's where the DD20 sits:
- PK20 (1.5 HP, 20 lbs, 7.5" flywheel): Lightest unit, flywheel included — for new builds where you want everything in one purchase
- DD20 (1.5 HP, 45 lbs, no flywheel, motor included): Same pump with motor pre-mounted, no flywheel — for rebuilds or custom builds where you already have a flywheel
- PK30 (1.5 HP, 45 lbs, 10" flywheel): Same 1.5 HP class with flywheel included
- PK50 (2 HP, 50 lbs, V2): Step up to 2 HP if your application demands it
- PK60 (3.5 HP, 55 lbs, V2): Mid-range for more CFM output
What This Pump Is Used For
A 1.5 HP single-cylinder pump produces enough CFM for light shop use — one air tool at a time, inflating tires, running a small brad nailer or stapler, or light blowing and cleaning tasks. It's not a production shop pump. It's appropriate for:
- Hobbyist and home garage compressors (tire inflation, light spraying, air tools with low CFM demand)
- Small portable compressor rebuilds where the original pump has failed and you want to maintain the original form factor
- OEM replacement on equipment built around this pump size
- Custom builds where 1.5 HP single-stage capacity fits the intended application
If you need more than one air tool running at a time, or you're running impact wrenches and air ratchets continuously, look at the 2 HP (PK50) or 3.5 HP (PK60) options.
What's in the Box
- DD20 cast iron pump assembly with motor pre-mounted
- 8 oz. oil capacity crankcase (oil not included)
Flywheel, tank, pressure switch, safety valve, gauges, air filter, and all plumbing are not included and must be sourced separately.
Installation Notes
- Castair recommends using Castair 30-weight non-detergent compressor oil
- Flywheel must match crankshaft specifications — verify before purchasing a flywheel separately
- Motor voltage and phase must match your electrical supply — contact us to confirm motor specs on this unit before ordering
- Warranty requires proper installation and maintenance per Castair's guidelines
Why Buy From Air Compressor Factory Direct?
- Specialist since 2016 — we stock Castair pumps and can help you confirm the DD20 fits your rebuild or build project
- Free shipping on qualifying orders
- Free tech support at 866-217-0063 — call before ordering if you're not certain about flywheel compatibility or motor specs
- Full manufacturer warranty — 1 year parts when properly installed
- Honest guidance — if you need a PK30 or PK50 instead, we'll tell you
Call 866-217-0063 for quick answers and help!
