The Castair DT12 is a 1/2-inch discharge tube assembly with fittings — a pre-built copper or steel discharge tube used to connect your air compressor pump's discharge outlet to the tank or downstream plumbing. The discharge tube handles the hottest, highest-pressure point in the compressor air path: right after the pump outlet, before the check valve and tank. At that location, air temperatures can exceed 300°F and pressure regularly hits the compressor's cutout pressure (typically 125–175 PSI depending on setup). This is not a job for rubber hose — you need a proper rigid discharge tube rated for the thermal and pressure conditions at pump discharge.
Why the Discharge Tube Matters
The discharge connection between the pump outlet and the tank is one of the most failure-prone points on any compressor. Common failure modes include:
- Rubber hose degradation: High-temperature air at pump discharge will cook rubber hose from the inside out over time. Cracks develop, hoses blow off under pressure, and you get a sudden loss of pressure and potential injury hazard.
- Vibration fatigue: The pump vibrates during operation. If the discharge connection is rigid pipe without any flex or vibration isolation, the fittings work-loosen over time and eventually crack or leak.
- Improper sizing: An undersized discharge tube creates backpressure that forces the pump to work harder and run hotter.
The DT12 is sized at 1/2 inch — appropriate for single-cylinder and smaller two-cylinder pumps where 1/2" discharge tubing matches the pump's outlet port size. For larger two-stage pumps, the 3/4" DT34 is the correct size.
What You Get
- 1/2" discharge tube — proper diameter for the pump outlet connection
- Fittings included — compression or threaded fittings to connect both ends of the tube
Note: Exact tube length, material (copper vs. steel), and fitting type details are not published in Castair's catalog for this part. The discharge tube page lists DT12 as "1/2-inch discharge tube with fittings" — contact us to confirm the exact length and configuration before ordering if your installation has specific dimension requirements.
Where This Part Is Used
The DT12 fits compressor builds and rebuilds using pumps with 1/2" discharge ports. Based on Castair's pump lineup, that covers the smaller single-cylinder pumps (PK20, DD20, PK30) and some smaller two-cylinder configurations. When you're rebuilding a pump, replacing a cracked or leaking discharge tube, or building a new compressor from components, the DT12 is the correct discharge tube for 1/2" outlet pumps.
Companion Parts
- DT34: 3/4" discharge tube — for larger pumps with 3/4" outlet ports
- CA1212: Compression adaptor 1/2"x1/2" — if you need to adapt tube to port size
- CE1212: Compression elbow 1/2"x1/2" — for directional routing
- CNS12: Compression nut and sleeve for 1/2" tube — for making additional compression connections
When to Replace Your Discharge Tube
- Any visible cracking, pitting, or corrosion on the tube body
- Leaking at either fitting connection that can't be stopped by tightening
- During any pump rebuild — if the pump is getting new valves and rings, replace the discharge tube at the same time
- If the existing tube is rubber — replace with the proper rigid discharge tube
Why Buy From Air Compressor Factory Direct?
- Specialist since 2016 — we stock Castair discharge tubes and fittings
- Free shipping on qualifying orders
- Free tech support at 866-217-0063 — call us to confirm the right discharge tube size for your pump
- Full manufacturer warranty on Castair parts
- Honest guidance — if you need the DT34 instead, we'll tell you
Call 866-217-0063 for quick answers and help!
