Castair S-20DP-150 Complete Air Filter Assembly — 1-1/2” Inlet, 60 CFM, Dual Foam Pre-Filter, Silencer Type
The Castair S-20DP-150 is the factory intake air filter assembly for cast iron compressor pumps with a 1-1/2” NPT inlet, rated at 60 CFM. This is the largest inlet size in the S-20DP body series. The "DP" designation means dual pre-filter construction — a foam pre-filter ahead of the primary 20DP element for extended service life in high-particulate shop environments. Body dimensions are 6.75” outer diameter and 7.0” overall height.
The 1-1/2” inlet is found on Castair larger cast iron pumps — the C4U and comparable models in the 15 HP range. The S-20DP-150 uses the same filter body as the S-20DP-100 and S-20DP-125 but with a 1-1/2” NPT inlet thread. Castair specifically notes that the 16DP, 20DP, and 32DP series filters include foam pre-filters as standard construction.
What the S-20DP-150 Does
- Foam pre-filter plus primary element: The foam pre-filter stage captures coarse airborne debris before it reaches the fine primary filter element. Extends element life in body shops, fabrication shops, or environments with higher airborne particulate loads.
- Silencer-type intake noise reduction: Attenuates the intake pulsation noise generated by the pump valve action. Meaningful improvement in ambient shop noise versus running without a silencer filter.
- Complete assembly with 20DP element: Ships ready to mount. Thread onto the 1-1/2” NPT pump inlet and tighten.
- 60 CFM rated flow: Matched to the displacement of 15 HP cast iron pump configurations. An undersized filter on a high-output pump creates inlet restriction and reduces pump efficiency and increases operating temperature.
Technical Specifications
- Part Number: S-20DP-150
- Manufacturer: Castair, Inc. (Spicer, MN)
- Inlet Connection: 1-1/2” NPT
- Outer Diameter: 6.75”
- Overall Height: 7.0”
- Flow Rating: 60 CFM
- Type: Silencer-type, dual pre-filter construction with foam pre-filter
- Replacement Element: 20DP (ID 3”, OD 4-3/8”, Height 4-3/4”)
- Compatible Pump: C4U and comparable cast iron pumps with 1-1/2” NPT inlets
Available Configurations — Castair Air Filter Lineup
- S-20DP-100 — 1” inlet, 6.75” OD x 7.0” height, 60 CFM
- S-20DP-125 — 1-1/4” inlet, 6.75” OD x 7.0” height, 60 CFM
- S-20DP-150 — 1-1/2” inlet, 6.75” OD x 7.0” height, 60 CFM (this unit — $71.61)
- S-32DP-200 — 2” inlet, 7.5” OD x 7.5” height, 195 CFM
When Does a Shop Need the S-20DP-150 vs. Stepping Up or Down?
- Order the S-20DP-150 if your pump inlet is 1-1/2” NPT and you are running a 15 HP class pump displacing up to 60 CFM.
- Confirm your inlet thread first: The S-20DP-100, -125, and -150 all use the same body at the same price. The only difference is inlet thread. A 1-1/2” filter will not fit a 1” or 1-1/4” port.
- Step up to S-32DP-200 for 20+ HP pumps with 2” NPT inlets and up to 195 CFM. The S-20DP body is not rated for that volume.
What’s in the Box
- 1x Castair S-20DP-150 complete air filter assembly (silencer type), 1-1/2” NPT inlet
- 1x 20DP filter element with foam pre-filter (pre-installed)
Why Buy From Air Compressor Factory Direct?
- Genuine Castair OEM parts — correct thread, correct element, correct fit
- Free shipping on qualifying orders
- Free tech support at 866-217-0063 — we confirm the correct inlet thread for your specific pump model before you order
- Full manufacturer warranty
- 20DP replacement elements in stock
Call 866-217-0063 for quick answers and help!
