The Caleffi 551004A is a DISCALAIR air vent with a 1/2 in NPT female connection and a brass body, used to automatically discharge air that collects at the high points of hydronic heating and cooling systems.
Product data compiled from Caleffi North America technical documentation. Last reviewed June 2026.
Key Features
Automatic Air Discharge
A float mechanism opens to release accumulated air automatically, then reseals as the system fills.
High-Point Venting
Installs at manifolds, separators and pump locations where air naturally collects.
High Discharge Pressure
Vents air against system pressure up to 150 psi maximum air discharge pressure.
Fast Purge Capacity
Maximum air discharge rate of 4.5 SCFM for rapid air removal.
1/2 In Npt Female Connection
1/2 in NPT female connection sized for the application.
Brass Construction
Brass body with stainless and EPDM internal components for hydronic service.
Technical Data
| Function | Automatic float air vent |
|---|---|
| Series | Caleffi DISCALAIR |
| Connection | 1/2 in NPT female |
| Body material | Brass |
| Maximum operating pressure | 150 psi |
| Maximum air discharge pressure | 150 psi |
| Maximum discharge rate | 4.5 SCFM |
| Medium temperature range | 32 - 230 °F |
Documentation
Technical brochureRelated Products
Frequently Asked Questions
At the high points of a hydronic system such as manifolds, air separators and pump locations, where air naturally collects.
An internal float drops as air accumulates, opening the discharge port; when water returns, the float rises and reseals the vent.
Up to 150 psi maximum air discharge pressure, with a 150 psi maximum operating pressure rating.
150 psi maximum operating pressure with a medium temperature range of 32 - 230 °F.
- Type:
- Air Vent
- Series:
- DISCALAIR
- Body Material:
- Brass
- Connection Type:
- NPT Threaded
- Connection Size:
- 1/2 in
