Unloader Valves | McMaster-Carr

	For Use With For Use With

	Inlet Pipe Size Inlet Pipe Size

	Outlet Pipe Size Outlet Pipe Size

	Maximum Inlet Pressure Maximum Inlet Pressure

	Inlet Thread Type Inlet Thread Type

NPT

UNF

	Seal Material Seal Material

Stainless Steel

Rubber

	Maximum Temperature Maximum Temperature

	Body Material Body Material

	Outlet Thread Type Outlet Thread Type

NPT

UNF

	Shape Shape


90° Elbow	Straight

	Outlet Pressure Adjustment Method Outlet Pressure Adjustment Method

Screw

Knob

T-Handle

	Minimum Temperature Minimum Temperature

-40° F

0° F

40° F

	Flow Coefficient (Cv) Flow Coefficient (Cv)

	Inlet Location Inlet Location

Bottom

Side

	Inlet Connection Style Inlet Connection Style

Threaded

Quick Clamp

	RoHS (Restriction of Hazardous Substances) RoHS (Restriction of Hazardous Substances)

RoHS Compliant with
Exemptions

RoHS Compliant

	DFARS (Defense Acquisition Regulations Supplement) DFARS (Defense Acquisition Regulations Supplement)

DFARS Specialty Metals
COTS-Exempt

	Outlet Connection Style Outlet Connection Style

Threaded

Quick Clamp

	Outlet Location Outlet Location

Side

Bottom

	Outlet Connection Type Outlet Connection Type


Pipe	Tube

	Inlet Connection Type Inlet Connection Type


Pipe	Tube

	Port-to-Port Length Port-to-Port Length

	REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) REACH (Registration, Evaluation, Authorization and Restriction of Chemicals)

REACH Compliant

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18 Products

Extended-Life Back-Pressure-Regulating Valves for Water and Oil

For Use With: Water, Oil
Temperature Range: -40° to 450° F

For a longer service than cast iron valves, these have a durable bronze body and a 303 stainless steel seal. Commonly installed as bypass lines after centrifugal, reciprocating, and rotary pumps, they obstruct flow to maintain sufficient operating pressure in your system. If the system pressure exceeds the set pressure, they exhaust through the outlet. Adjust the set pressure within the range.

For technical drawings and 3-D models, click on a part number.

Inlet			Outlet
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	Port-to-Port Lg.	Choose an Outlet Pressure Range, psi		Each
NPT Female
Bronze Body—303 Stainless Steel Seal
1/4	Bottom	600	1/4	Side	1 1/4"	15 to 30, 25 to 75, 50 to 140, 100 to 300, 200 to 600	0000000	0000000
3/8	Bottom	600	3/8	Side	1 1/4"	15 to 30, 25 to 75, 50 to 140, 100 to 300, 200 to 600	0000000	000000
1/2	Bottom	600	1/2	Side	1 5/8"	15 to 75, 50 to 150, 100 to 300, 200 to 600	0000000	000000
3/4	Bottom	600	3/4	Side	1 5/8"	15 to 75, 50 to 150, 100 to 300, 200 to 600	0000000	000000
1	Bottom	600	1	Side	2 1/4"	15 to 75, 50 to 150, 100 to 300, 200 to 600	0000000	000000
1 1/4	Bottom	600	1 1/4	Side	2 1/4"	15 to 75, 50 to 150, 100 to 300, 200 to 600	0000000	000000

Back-Pressure-Regulating Valves for Water and Oil

For Use With: Water, Oil
Temperature Range: -40° to 200° F

Commonly used as bypass lines after centrifugal, reciprocating, and rotary pumps, these valves obstruct flow to maintain sufficient operating pressure in your system. If the system pressure exceeds the set pressure, they exhaust through the threaded relief port. Adjust the set pressure within the range. Valves have a cast iron body that absorbs vibration from pressure changes to reduce wear and noise in your pipeline.

For technical drawings and 3-D models, click on a part number.

Inlet			Outlet		Relief Port
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	Pipe Size	Location	End-to-End Lg.	Choose an Outlet Pressure Range, psi		Each
NPT Female
Cast Iron Body—Nickel Alloy Diaphragm and 303 Stainless Steel Seal
1/2	Side	400	1/2	Side	1/2	Bottom	2 7/8"	0 to 25, 5 to 50, 30 to 100, 75 to 175, 150 to 400	0000000	0000000
1 1/4	Side	400	1 1/4	Side	1 1/4	Bottom	4 1/4"	20 to 85, 40 to 125, 50 to 230, 175 to 380, 300 to 400	0000000	00000000
1 1/2	Side	400	1 1/2	Side	1 1/2	Bottom	5"	10 to 55, 30 to 100, 40 to 200, 125 to 300, 200 to 400	0000000	00000000
2	Side	400	2	Side	2	Bottom	5"	10 to 55, 30 to 100, 40 to 200, 125 to 300, 200 to 400	0000000	00000000

Panel-Mount Back-Pressure-Regulating Valves for Air and Inert Gas

For Use With: Air, Inert Gas
Temperature Range: 40° to 150° F

Threads below the adjustment knob and an included panel-mount nut allow you to add these valves to your instrument panel. Often used in systems running on air compressors, they're installed after pressure-sensitive equipment to obstruct flow and maintain a consistent operating pressure. If the system pressure exceeds the set pressure, they exhaust through the outlet. Adjust the set pressure within the range.

For technical drawings and 3-D models, click on a part number.

Inlet				Outlet
Pipe Size	Thread Size	Location	Max. Pressure, psi	Pipe Size	Thread Size	Location	End-to-End Lg.	Panel Cutout Dia.	Choose an Outlet Pressure Range, psi		Each
NPT Female
Polysulfone Body—Buna-N Diaphragm and Silicone Seal
1/8	__	Side	100	1/8	__	Side	1 1/8"	9/16"	0.5 to 3.5, 0.5 to 10, 0.5 to 30, 0.5 to 60, 0.5 to 90	00000000	000000
UNF Female
Polysulfone Body—Buna-N Diaphragm and Silicone Seal
__	10-32	Side	100	__	10-32	Side	1 1/8"	9/16"	0.5 to 3.5, 0.5 to 10, 0.5 to 30, 0.5 to 60, 0.5 to 90	00000000	00000

Back-Pressure-Regulating Valves for Air and Inert Gas

For Use With: Air, Inert Gas
Temperature Range: 0° to 150° F

Often used to protect equipment running on air compressors, these valves obstruct flow to maintain sufficient operating pressure in your system. If the system pressure exceeds the set pressure, they exhaust through the unthreaded relief port. Adjust the set pressure within the range. Valves have two gauge ports.

For technical drawings and 3-D models, click on a part number.

Inlet			Outlet		Gauge Port
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	Pipe Size	Location	End-to-End Lg.	Choose an Outlet Pressure Range, psi		Each
NPT Female
Aluminum Body—Buna-N Diaphragm and Seal
1/4	Side	250	1/4	Side	1/4	Side	3"	0 to 2, 0 to 10, 0 to 30, 0 to 60, 0 to 150	0000000	0000000
3/8	Side	250	3/8	Side	1/4	Side	3"	0 to 2, 0 to 10, 0 to 30, 0 to 60, 0 to 150	0000000	000000
1/2	Side	250	1/2	Side	1/4	Side	3"	0 to 2, 0 to 10, 0 to 30, 0 to 60, 0 to 150	0000000	000000

Sanitary Back-Pressure-Regulating Valves

For Use With: Food and Beverage
Temperature Range: -40° to 120°F
Specifications Met: 3-A Certified 64-00, ANSI/FCI 70-2 Class III, FDA Compliant 21 CFR 177.2600

Designed to meet 3-A sanitary standards, these valves regulate liquid, gas, and air pressure in hygienic zones of food and beverage plants. They’re often used at the end of pipelines on processing and sanitizing equipment. Made of 316 stainless steel, they won't corrode from frequent washdowns with harsh cleaners. With an extremely smooth interior that self-drains, bacteria won't have time or space to grow. The spring and internal valve mechanisms are sealed off behind the diaphragm, which also prevents contamination. They connect with quick-clamp fittings, so disassembling to clean your line takes little time.

These valves obstruct flow to maintain sufficient operating pressure in your system. If the system pressure exceeds the set pressure, they exhaust through the outlet. They meet ANSI/FCI 70-2 Class III standards for shut-off valves, meaning a maximum of 0.1% of fluid, gas, or air will escape through the outlet when they’re closed. An integrated T-handle lets you set the outlet pressure without additional tools. The diaphragm and seal resist repeated exposure to water, and they’re FDA compliant for direct contact with food.

For technical drawings and 3-D models, click on a part number.

Inlet				Outlet			Lg.
For Tube OD	Flange OD	Location	Max. Pressure, psi	For Tube OD	Flange OD	Location	End-to-End	Port-to-Port	Choose an Outlet Pressure Range, psi		Each
Quick Clamp
316 Stainless Steel Body—EPDM Diaphragm and EPDMSeal
3/4"	0.984"	Side	200	3/4"	0.984"	Bottom	6 5/8"	3 9/32"	5 to 30, 35 to 90, 50 to 105	000000	000000000
1"	1.984"	Side	200	1"	1.984"	Bottom	6 11/16"	3 5/16"	5 to 30, 35 to 90, 50 to 105	000000	00000000
316 Stainless Steel Body—PTFE Plastic Diaphragm and EPDMSeal
2"	2.516"	Side	100	2"	2.516"	Bottom	11 5/8"	5 3/4"	10 to 25, 15 to 60	000000	00000000