The Caleffi 553642A is an AutoFill pre-adjustable automatic filling valve with a 1/2 in NPT inlet x 1/2 in NPT outlet connection with integral pressure gauge, a pressure-reducing valve that automatically maintains the set fill pressure in a closed hydronic heating or cooling system.
Product data compiled from Caleffi North America technical documentation. Last reviewed July 2026.
Key Features
Pre-Adjustable Fill Pressure
Set the target system pressure before installation; the valve automatically reduces and holds it as the system fills.
Automatic Make-Up Water
Restores system pressure automatically after air venting or minor losses, keeping the loop full without manual attention.
Serviceable Cartridge
The internal cartridge is removable for cleaning or replacement without unsoldering the valve body.
3-60 psi Adjustment Range
Downstream set-point adjustable across 3-60 psi.
Integral Pressure Gauge
A built-in gauge shows the set fill pressure at a glance.
Technical Data
| Function | Pre-adjustable automatic filling valve (pressure reducing) |
| Connection | 1/2 in NPT male union inlet x 1/2 in NPT female outlet |
| Pressure gauge | Included |
| Adjustment pressure range | 3-60 psi |
| Maximum working pressure | 230 psi |
| Factory pressure setting | 15 psi |
| Maximum working temperature | 150 °F |
| Pressure gauge scale | 0-60 psi |
| Material | brass |
Documentation
Technical brochureRelated Products
- Caleffi 553542A 1/2 in Auto Fill Valve
- Caleffi 553549A 1/2 in Auto Fill Valve
- Caleffi 553649A 1/2 in Auto Fill Valve
- Caleffi 573002A 1/2 in ASSE 1012 Fill + Backflow Combo
Frequently Asked Questions
What does the Caleffi 553642A do?
It is a pre-adjustable automatic filling valve: a pressure-reducing valve that fills a closed hydronic system to a set pressure and automatically restores it as needed.
How do I set the fill pressure?
Adjust the set point within the 3-60 psi range using the adjustment knob; on gauge models the set pressure is visible directly on the valve.
Does it include backflow prevention?
No. This is the filling valve only. For code-required backflow protection, use an AutoFill Combo, which pre-assembles the fill valve with an ASSE-listed backflow preventer.
- Type:
- Automatic Filling Valve
- Series:
- AutoFill
- Pressure Gauge:
- Included
- Connection Type:
- NPT Threaded
- Connection Size:
- 1/2 in
