The Caleffi 535951HA is a PresCal 535H series pre-adjustable pressure reducing valve with 3/4" Sweat union connections. It reduces and stabilises incoming water main pressure to an adjustable outlet setting between 15 and 90 psi, factory set at 45 psi, and is rated to 300 psi maximum working pressure at up to 180°F. A dial indicator lets the set point be pre-adjusted before installation.
Best for residential and commercial service entrances where code requires pressure control above 80 psi, and for jobs where the valve is set on the bench before it goes in the line.
Caleffi 2-Year Limited Warranty. Caleffi North America warrants each Caleffi product free from defects in material and workmanship for two years from the date of shipment or delivery. Repair, replacement or refund of the purchase price is at Caleffi's discretion and is the sole remedy. Full terms are set out in the Caleffi North America Limited Warranty. ZOT Supply is a Caleffi distributor.
Key Features
Pre-Adjustable Set Point Dial
The set point indicator reads from both sides of the valve and steps in 15 psi increments, so the outlet pressure can be dialled in before the valve ever goes in the line. A screw in the top of the knob locks the setting against tampering.
Removable Self-Contained Cartridge
Diaphragm, filter, seat, shuttle and compensating piston come out as one pre-assembled unit with its cover. Servicing does not disturb the set point and does not require the body to leave the piping. Replacement cartridge 535006HA covers 1/2, 3/4 and 1 inch valves.
35 Mesh Stainless Strainer
An integral 0.51 mm AISI 304 stainless filter sits inside the cartridge, protecting the seat on supply water carrying sediment or pipe debris.
Chloramine-Resistant EPDM
The diaphragm and seals are peroxide-cured EPDM, which resists water treated with chlorine or chloramine for longer service life than standard elastomers.
UV Outdoor Protective Cover
Every 535H ships with a UV-stabilised ABS cover for outdoor service. With the cover removed the valve is plenum rated, evaluated to and found compliant with UL 2043.
POSI-STOP Unions, Inlet and Outlet
Union seals on both ports let the valve come out for cartridge service without cutting pipe or disturbing adjacent fittings.
Technical Specifications
| Product Type | Pressure Reducing Valve |
| Product Series | PresCal 535H |
| Valve Type | Diaphragm type, pre-adjustable |
| Connection Size | 3/4" |
| Connection Type | Sweat union |
| Union Configuration | Dual union (POSI-STOP inlet and outlet) |
| Outlet Pressure Range | 15-90 psi (100-600 kPa) |
| Factory Setting | 45 psi (300 kPa) |
| Maximum Working Pressure | 300 psi (2000 kPa) |
| Maximum Working Temperature | 180°F (80°C) |
| Flow Rate at 6 fps | 12.5 gpm |
| Suitable Fluids | Water |
| Pressure Gauge | Factory-fitted 0-100 psi outlet gauge |
| Pressure Gauge Connection | 1/8" NPT female |
| Filter Mesh Size | 0.51 mm (35 mesh), stainless steel AISI 304 |
| Body Material | DZR low-lead forged brass |
| Housing | Glass reinforced nylon PA66M40/1 |
| Outdoor Cover | UV stabilised ABS, gray (supplied) |
| Diaphragm and Seals | Peroxide-cured EPDM |
| Seat | Stainless steel AISI 303 |
| Certifications | ICC-ES certified to ASSE 1003 and CSA B356 (R2015); NSF/ANSI/CAN 61 (180°F/82°C Commercial Hot), file PMG-1356; NSF/ANSI/CAN 372, file PMG-1360 |
| Code Compliance | IPC, IRC, UPC, NPC |
| Plenum Rating | UL 2043 compliant, outdoor cover removed |
| Shipping Weight | 2.3 lb |
Specifications taken from Caleffi datasheet 01265/23.1 NA, installation instructions NA10397.07 and submittal data 03020 NA.
Documentation
Design Resources
Related Products
- Caleffi 535351HA : PresCal Pressure Reducing Valve 3/4" NPT w/ Gauge
- Caleffi 535651HA : PresCal Pressure Reducing Valve 3/4" Press w/ Gauge
- Caleffi 535751HA : PresCal Pressure Reducing Valve 3/4" PEX Crimp w/ Gauge
- Caleffi 535950HA : PresCal Pressure Reducing Valve 3/4" Sweat
- Caleffi 535006HA : Replacement Cartridge, 535H 1/2, 3/4 and 1 inch
Frequently Asked Questions
What does the Caleffi 535951HA do?
The 535951HA is a PresCal 535H series pressure reducing valve. It lowers incoming water main pressure to a stable, adjustable outlet pressure between 15 and 90 psi, protecting fixtures, appliances and piping. Plumbing codes generally require a pressure reducing valve where static supply pressure exceeds 80 psi.
What makes the 535H pre-adjustable?
A dial indicator on the operating knob reads the set point from either side of the valve and displays it in 15 psi increments. The pressure can be set to the required value before installation, and the valve controls at that setting once in service.
Is the Caleffi 535951HA certified for potable water?
Yes. It is ICC-ES certified to ASSE 1003 and CSA B356 (R2015), complies with NSF/ANSI/CAN 61 for 180°F/82°C Commercial Hot under file PMG-1356, and complies with NSF/ANSI/CAN 372 under file PMG-1360. It meets IPC, IRC, UPC and NPC.
What is the maximum inlet pressure for the 535951HA?
300 psi (2000 kPa). PTFE rings on the compensating piston allow continuous duty at upstream pressures up to that figure. Where the ratio between inlet and outlet pressure is too high for one valve to control, Caleffi calls for a two-stage arrangement with a 536A series PresCal HP as the first stage.
Does the Caleffi 535951HA include a pressure gauge?
Yes. A 0-100 psi outlet gauge is factory fitted. For the same valve without a gauge, order 535950HA.
Can the 535951HA be installed outdoors or in a plenum?
Every 535H model ships with a UV-stabilised ABS protective cover for outdoor installation. Without that cover the valve was evaluated to UL 2043 and found compliant, so it may be used in air-handling plenums.
- Product Type:
- Pressure Reducing Valve
- Valve Type:
- Diaphragm
- Product Series:
- PresCal
- Outlet Pressure Range:
- 15-90 psi
- Pressure Gauge:
- Included
- Connection Type:
- Sweat
- Connection Size:
- 3/4 inch
- Union Configuration:
- Dual Union
- Certification:
- ASSE 1003
- Max Operating Pressure:
- 300 psi
- Body Material:
- DZR low lead brass
