The Caleffi 548009US 001 is a hydraulic separator with 2" union-body (supplied without tailpieces) connections, rated for 37 gpm at a maximum working pressure of 150 psi. It installs between the heat source circuit and the distribution circuits of a hydronic heating or chilled water system to provide hydraulic separation.
Caleffi specifies this series for hydronic heating and chilled water systems containing a primary production circuit with its own pump and a secondary user circuit with one or more distribution pumps, where pump interaction would otherwise cause abnormal variations in circuit flow rates and pressures. Caleffi states the separator should be sized to the greater of the primary or secondary circuit flow rate; this model is rated for 37 gpm. Source: 01076/24 NA, Operating principle and Hydraulic characteristics.
Key Features
Primary/Secondary Hydraulic Decoupling
A low pressure-loss zone lets the boiler circuit and the distribution circuits operate independently, so neither pump interferes with the other. Rated for 37 gpm.
High-Capacity Automatic Air Vent
A float-operated brass automatic air vent continuously discharges air that collects at the top of the vessel, with no manual venting routine required.
Blowdown Drain Valve
A brass drain valve at the base of the vessel purges settled impurities without taking the system offline.
Wall Mounting Bracket Included
A polyester painted carbon steel support bracket ships with the separator for direct wall mounting. Pre-formed PE-X insulation is available separately for field installation.
Technical Specifications
| Product Line | Hydro Separator |
| Series | 548 |
| Connection Size | 2" |
| Connection Type | Union Body, No Tailpieces |
| Connection Style | Union |
| Separation Functions | Hydraulic separation |
| Rated Flow | 37 gpm |
| Fluid Volume | 3.5 gal |
| Maximum Working Pressure | 150 psi (10 bar) |
| Working Temperature Range, Uninsulated | 32 - 250 °F (120 °C) |
| Working Temperature Range, Insulated | 32 - 210 °F (0 - 100 °C) |
| Suitable Fluids | Water and non-hazardous glycol solution to 50% |
| Body Material | Epoxy resin painted steel |
| Internal Element Material | 300 series stainless steel |
| Union Nut Material | Cast iron |
| Drain Valve | 3/4" garden hose thread |
| Thermowell Tap | 1/2" female straight thread |
| Support Bracket | Polyester painted carbon steel, included |
| Insulation | Not included; field-installed PE-X jacket available separately |
| Supplied As | Separator body only, without tailpieces or union nuts |
| Product Weight | 27 lb |
Specifications on this page are taken from Caleffi North America technical brochure 01076/24 NA and the associated submittal and installation documents linked below. The US suffix is defined in 01076/24 NA page 1, which lists 54800xUS as the body supplied without tailpieces; the size digit follows the same dimension table as the 54800x union models. Last verified July 2026.
Documentation
Design Resources
Related Products
- Caleffi 548009A : Hydro Separator 2" NPT Union
- Caleffi 548099A : Hydro Separator 2" Sweat Union
- Caleffi 548069A : Hydro Separator 2" Press Union
- Caleffi 548052A : Hydro Separator 2" ANSI Flanged
- Caleffi NA10797 : Wall Mounting Bracket for 2" Union 548 and 5495 Separators
- Caleffi NA10425 : Temperature Pocket Well Kit for 548 and 5495 Union Separators
Frequently Asked Questions
What does the Caleffi 548009US 001 do in a hydronic system?
The Caleffi 548009US 001 is a hydraulic separator with 2" union-body (supplied without tailpieces) connections. It creates a low pressure-loss zone between the boiler circuit and the distribution circuits so that each pump works only against its own loop, which eliminates pump conflict without relying on closely spaced tees. It is rated for 37 gpm and holds 3.5 gallons.
Does the Caleffi 548009US 001 separate air and dirt?
The 548009US 001 is a hydraulic separator. It includes a high-capacity automatic air vent to discharge accumulated air and a blowdown drain valve to purge settled impurities, but it does not carry the coalescing dirt element rated to 5 microns or the magnetic element found on the Caleffi HydroCal and SEP4 series.
What flow rate is the Caleffi 548009US 001 rated for?
Caleffi rates the 2" 548009US 001 at 37 gpm with a fluid volume of 3.5 gallons. A hydraulic separator should be sized to the greater of the primary or secondary circuit design flow rate, not to the pipe size alone.
Is the Caleffi 548009US 001 ASME code stamped?
No. The 548009US 001 is rated for 150 psi maximum working pressure but is not ASME code stamped. Where a project specification calls for an ASME stamped and National Board registered vessel, use the corresponding Caleffi NA-prefix model.
Does the Caleffi 548009US 001 come with insulation?
No. Union-connection separators ship with a wall mounting bracket but without insulation. A pre-formed closed-cell PE-X jacket sized for this model is available separately for field installation.
- Type:
- Hydraulic Separator
- Separation Functions:
- Hydraulic
- Product Line:
- Hydro Separator
- Series:
- 548
- Connection Style:
- Union
- ASME Code Stamped:
- No
- CRN Registered:
- No
- Insulation Included:
- No
- Connection Type:
- Union Body No Tailpieces
- Connection Size:
- 2 inch
- Max Operating Pressure:
- 150 psi
