The Castair 16D is a replacement air filter element for the S-16D-075 assembly, designed for Castair A4 and A8 series compressor pumps. This is a standard maintenance item for single-stage industrial Castair compressors in the 3.5-5 HP range. At $7.70 per element, it is one of the lowest-cost maintenance items in the Castair system — and one of the more important ones. Running with a dirty or missing intake filter restricts airflow and accelerates pump wear.
Filter Element Specifications
- Part Number: 16D
- Fits Assembly: S-16D-075 (3/4" inlet silencer/filter assembly)
- Compatible Pumps: A4 and A8 series (also fits S-16D-100 assembly per filter chart)
- Inner Diameter: 3 inches
- Outer Diameter: 4-3/8 inches
- Height: 2-1/8 inches
- Pre-filter: No — standard element without foam pre-filter
- Price: $7.70 per element
16D vs. 16DP: Choosing the Right Element
Both elements have identical physical dimensions — 3" ID, 4-3/8" OD, 2-1/8" height. The key differences:
- 16D ($7.70): Fits S-16D-075 (3/4" inlet assembly). Used on A4/A8 pumps (single-stage, 3.5-5 HP). No foam pre-filter.
- 16DP ($10.01): Fits S-16D-100 (1" inlet assembly). Used on C1, C2, C3U pumps (two-stage, 4-15 HP). Includes foam pre-filter.
The 16D is for smaller single-stage pumps; the 16DP is for larger two-stage pumps. Ordering the wrong element is a common mistake — confirm your pump model before ordering. The A4 and A8 are single-stage, V-twin configuration pumps in the 3.5-5 HP range used in Castair commercial and some industrial units.
About the A4 and A8 Pumps
- A4: Single-stage pump in the 3.5-5 HP class, used in Castair commercial-series compressors
- A8: Similar single-stage pump, higher CFM variant — the VA80 designation in Castair's pump lineup (3.5-5 HP, 110 lbs, single-stage)
- Both pumps use a 3/4" inlet, which matches the S-16D-075 assembly that takes the 16D element
Why Intake Air Filtration Matters
The intake filter removes airborne particulates before they enter the pump cylinders. Fine dust, metal particles, and shop debris are abrasive inside pump cylinders and on valve seats. A clean filter means cleaner air going in and less wear on internal pump components. Beyond protecting the pump, the silencer housing also reduces intake noise — a secondary benefit that makes the compressor quieter during operation. Both functions degrade when the filter element is clogged or missing.
Maintenance Schedule
Inspect the 16D element every oil change. In clean environments, annual replacement is typically sufficient. In dusty shops, inspect every 3 months and replace when visibly dirty. The element cannot be cleaned with compressed air (paper media) — replace it when dirty.
Castair Right From The Start Kits
The Castair RFS001 and RFS002 start-up kits include two 16D elements per kit. If you bought your compressor with a Right From The Start kit, those were your initial elements. Replacement 16D elements are ordered individually or in any quantity from us.
What's in the Box
- 1x Castair 16D replacement air filter element
Note: The S-16D-075 filter housing is sold separately. Element replacement requires no special tools in most applications — remove the housing cap, pull the old element, insert the new one, reinstall the cap.
Why Buy From Air Compressor Factory Direct?
We carry the full range of Castair replacement parts and maintenance supplies. Filter elements ship fast and free. If you are building a maintenance kit for a Castair compressor, call us — we can put together everything you need (oil, filters, belts) in one order. Free shipping, free technical support at 866-217-0063, and full manufacturer warranty on all Castair parts.
Call 866-217-0063 for quick answers and help!
