Castair S-20DP-100 Complete Air Filter Assembly — 1” Inlet, 60 CFM, Dual Foam Pre-Filter, Silencer Type
The Castair S-20DP-100 is the factory intake filter assembly for high-output cast iron compressor pumps with a 1” NPT inlet rated at 60 CFM. This is a step up in both capacity and filtration design from the S-16D series. The "DP" designation indicates dual pre-filter construction — this assembly uses a foam pre-filter ahead of the primary element, which extends element service life in dusty shop environments. The body is 6.75” outer diameter by 7.0” overall height — taller than the S-16D series to accommodate the higher CFM and dual-stage filter media.
At 60 CFM rated throughput, this filter is sized for 10–15 HP cast iron pump configurations. Castair industrial-series 10 HP models produce 45 CFM at displacement and 35 CFM at 175 PSI. The S-20DP-100 handles that throughput with margin at the 1” NPT inlet size. Per Castair cross-reference, it is specified for the C4U pump model.
What the S-20DP-100 Does
- Dual-stage filtration: The foam pre-filter captures large particulates before they reach the primary 20DP element. This extends element service intervals and provides better protection in high-dust environments — body shops, woodworking shops, fabrication environments.
- Silencer construction: The "S" prefix means this assembly attenuates intake noise. At 60 CFM throughput on a slow-RPM industrial pump, intake noise reduction is noticeable.
- Complete assembly: Ships ready to mount with the 20DP element and foam pre-filter already installed.
- 60 CFM rated capacity: Handles the full displacement of 10–15 HP Castair industrial pumps without creating inlet restriction. An undersized filter on a high-output pump limits performance and causes overheating.
Technical Specifications
- Part Number: S-20DP-100
- Manufacturer: Castair, Inc. (Spicer, MN)
- Inlet Connection: 1” 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”) — includes foam pre-filter
- Compatible Pump: C4U (per Castair cross-reference)
Compatible Applications
- Castair C4U cast iron pump with 1” NPT inlet
- Castair industrial series compressors 10–15 HP with 1” NPT pump inlets displacing up to 60 CFM
- Any reciprocating compressor pump with a 1” NPT inlet displacing up to 60 CFM at operating pressure
Replacement Element: 20DP
- Element Part Number: 20DP
- Inner Diameter: 3”
- Outer Diameter: 4-3/8”
- Height: 4-3/4”
- The 20DP element is taller than the 16D and includes a foam pre-filter layer. Do not substitute a 16D element in an S-20DP body — it is shorter and will not seat correctly.
Available Configurations — Castair Air Filter Lineup
- S-16D-100 — 1” inlet, 6.75” OD x 4.5” height, 30 CFM (smaller body, lower CFM)
- S-20DP-100 — 1” inlet, 6.75” OD x 7.0” height, 60 CFM (this unit — $71.61)
- 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
- S-32DP-200 — 2” inlet, 7.5” OD x 7.5” height, 195 CFM
When Does a Shop Need the S-20DP-100 vs. Stepping Up or Down?
- Order the S-20DP-100 if your pump has a 1” NPT inlet and your compressor is 10–15 HP, displacing more than 30 CFM. The S-16D-100 also takes a 1” NPT inlet but is only rated at 30 CFM.
- Step down to S-16D-100 if your 1” inlet pump displaces only up to 30 CFM. You do not need the taller 20DP body.
- Step up to S-20DP-125 or S-20DP-150 if your pump inlet is 1-1/4” or 1-1/2” NPT at the same 60 CFM range. Same body, larger inlet thread.
- Step up to S-32DP-200 for 20–30 HP pumps with 2” inlets and up to 195 CFM displacement.
What’s in the Box
- 1x Castair S-20DP-100 complete air filter assembly (silencer type), 1” NPT inlet
- 1x 20DP filter element with foam pre-filter (pre-installed)
Why Buy From Air Compressor Factory Direct?
- Genuine Castair OEM component — correct for the C4U pump per manufacturer specification
- Free shipping on qualifying orders
- Free tech support at 866-217-0063 — call if uncertain whether your pump takes S-16D-100 or S-20DP-100
- Full manufacturer warranty
- 20DP replacement elements stocked
Call 866-217-0063 for quick answers and help!
