Drains collect and discharge condensate from receivers, filters, dryers, and drip legs. Failed drains are the #1 cause of wet air.
Key specs
- Float / mechanicalLow cost, prone to fouling, no air loss when working
- Timer solenoidSimple, wastes air on dry cycles, predictable
- Zero-loss (electronic level)No air loss, alarm contact, best for energy
Installation
- Always install with isolation ball valve upstream — drains will need service.
- Pipe discharge to oil-water separator. Compressed air condensate is regulated waste in most jurisdictions.
- Drain receiver from low point with strainer ahead of drain.
Preventive maintenance
- Weekly: open manual bypass to confirm collection point isn't loaded.
- Monthly: clean strainer, test alarm contact (zero-loss models).
- Annual: rebuild kit on solenoid drains; replace level sensors as needed.
Troubleshooting
Drain not discharging
Likely causes
- Plugged strainer
- Failed solenoid coil
- Stuck float
- Iced discharge line in winter
Fix
Clean strainer, replace coil, heat-trace outdoor discharge lines.
Drain blowing continuously
Likely causes
- Stuck-open solenoid
- Failed level sensor
- Bypass valve left open
Fix
Replace solenoid/sensor, close bypass.