The Caleffi NA553372 is an NA553 boiler trim kit that packs eight boiler-room components into one box: a 1-1/4 in NPT DISCAL air separator (code 551007A), an AutoFill automatic filling valve pre-assembled with a ASSE 1012 dual-check backflow preventer with atmospheric vent (code 573002A, 1/2 in NPT), a 4.4-gallon pre-pressurized expansion tank, an expansion tank check valve (code 561402A), two 3 in brass nipples and a brass NPT tee.
Product data compiled from Caleffi North America technical documentation. Last reviewed July 2026.
Key Features
Eight Components, One Box
DISCAL air separator 551007A (1-1/4 in NPT) · AutoFill + ASSE 1012 backflow combo 573002A (1/2 in NPT) · 4.4 gal expansion tank · expansion tank check valve 561402A · two 3 in brass nipples · brass NPT tee. Caleffi matches every part for the installation, so nothing is sourced separately.
ASSE 1012 Backflow Preventer
Includes an ASSE 1012 dual-check backflow preventer with atmospheric vent for typical residential boiler feed.
4.4-Gallon Expansion Tank
A pre-pressurized diaphragm expansion tank absorbs the expansion volume of the heated system fluid.
Fewer Joints, Faster Install
Factory-matched components cut sourcing time and field assembly on new boiler installations.
Technical Data
| Function | Boiler trim kit (filling valve, backflow preventer, expansion tank) |
| ASSE listing | ASSE 1012 |
| Air separator | Caleffi DISCAL 551007A, 1-1/4 in NPT |
| Fill / backflow combo | Caleffi 573002A, 1/2 in NPT, ASSE 1012 |
| Expansion tank check valve | Caleffi 561402A |
| Connection | 1-1/4 in NPT (air separator); 1/2 in NPT (fill / backflow) |
| Expansion tank | 4.4 gallon |
| Nipples and tee | Two 3 in brass nipples, one brass NPT tee |
Documentation
Technical brochureRelated Products
- Caleffi NA553372R 1-1/4 in ASSE 1013 Boiler Trim Kit
- Caleffi NA553376 1-1/4 in ASSE 1012 Boiler Trim Kit
- Caleffi NA553376R 1-1/4 in ASSE 1013 Boiler Trim Kit
Frequently Asked Questions
What is included in the NA553372 kit?
Eight components: a 1-1/4 in NPT DISCAL air separator (551007A), an AutoFill filling valve pre-assembled with a ASSE 1012 backflow preventer (573002A, 1/2 in NPT), a 4.4-gallon pre-pressurized expansion tank, an expansion tank check valve (561402A), two 3 in brass nipples and a brass NPT tee.
Which backflow preventer does it use?
An ASSE 1012 dual-check with atmospheric vent for typical residential boiler feed.
What size is the expansion tank?
4.4 gallons, pre-pressurized, sized for typical residential boiler applications.
- Type:
- Boiler Trim Kit
- ASSE Standard:
- ASSE 1012
- Connection Type:
- NPT Threaded
- Connection Size:
- 1-1/4 in
