Double Union Check Valve

Overview of Double Union Check Valve​

Sikerui Double Union Check Valve​ is a highly efficient backflow prevention device that integrates two independent check mechanisms​ within a single unit, featuring union connections on both ends for easy installation and maintenance . This valve is engineered to protect piping systems from reverse flow contamination by employing a redundant sealing design—if the primary check fails, the secondary check provides immediate backup protection . Manufactured to international standards including ASSE, AWWA, and EN, these valves are available in materials such as bronze, stainless steel, PVC, and ductile iron, catering to pressures up to 3000 PSI and temperatures from -40°C to 250°C . The union ends enable tool-free disassembly for inspection or cleaning, making these valves ideal for applications where maintenance downtime must be minimized . Commonly used in potable water systems, industrial processes, fire protection, and irrigation networks, double union check valves offer a reliable, testable, and code-compliant solution for low-to-medium hazard scenarios . Their robust construction ensures long service life with minimal upkeep, providing critical protection for water quality and system integrity.

Key Features of Double Union Check Valve​

1. Redundant Backflow Prevention​
   The valve incorporates two independently operating check modules​ arranged in series, ensuring that if one mechanism fails due to debris or wear, the second mechanism activates to block reverse flow . This dual-seal design is certified for fluid category 3 protection (low-toxicity substances) and complies with industry standards for backflow prevention in potable water applications.
2. Easy Maintenance with Union Connections​
   Union ends on both sides​ allow quick disconnection of the valve without cutting pipes or disturbing adjacent piping . This design simplifies routine inspections, seal replacements, and cleaning, reducing system downtime by up to 50% compared to fixed-installation valves.
3. Testable Design for Compliance​
   Equipped with test cocks on both check modules, the valve enables in-line verification of sealing performance without removal . This feature is essential for annual compliance testing mandated by plumbing codes in commercial and municipal systems.
4. Versatile Material Compatibility​
   Constructed from corrosion-resistant materials​ like bronze for water services, stainless steel for chemicals, or PVC for cost-effective irrigation, the valve adapts to various media . Optional epoxy coatings or specialty seals (EPDM, Viton) extend suitability for aggressive fluids or extreme temperatures.
5. Low Pressure Drop and High Flow Efficiency​
   The full-bore design​ of check modules minimizes flow resistance, reducing energy consumption in pumping systems . This is critical in high-flow applications like fire sprinkler networks or water distribution, where pressure preservation is essential.

Typical Applications of Double Union Check Valve​

• Potable Water Systems: Installed at service connections​ to prevent backflow from commercial buildings or irrigation systems into municipal water mains . The redundant design meets code requirements for cross-connection control in low-hazard scenarios.
• Fire Protection Systems: Used in sprinkler and standpipe installations​ to avoid reverse flow of stagnant water into clean supply lines . The testable design allows annual verification required by insurance and safety standards.
• Industrial Processes: Protects cooling towers, boiler feed lines, and chemical injection points​ from contamination . Stainless steel or alloy versions resist corrosion from process media while union ends facilitate quick module replacement.
• Irrigation and Agricultural Systems: Prevents fertilizer or pesticide backflow​ into potable water sources, with PVC versions offering UV resistance and cost efficiency for outdoor use . The dual checks provide reliability in remote or automated watering systems.

Technical Specifications​

Table: Standard Double Union Check Valve Specifications

Number	Name	Material	Quantity	Unit
1	Socket/Socket End	UPVC/CPVCPPH	2	PCS
2	Nut	UPVC/CPVCPPH	2	PCS
3	Gasket	EPDMVTON	1	PCS
4	Spacer​	UPVC/CPVCPPH	1	PCS
5	Ball	UPVC/CPVCPPH	1	PCS
6	O-Ring	EPDMVTON	1	PCS

 

SIZE	d	d1					d2					D	L	L1
		UPvcCPvc				PPH	UPvcCPvc				PPH
		ANSI	DIN	JIS	CNS	DIN	ANSI	DIN	JIS	CNS	DIN
1/2″(DN15)	17.00	21.40	20.25	22.30	22.40	19.30	21.25	20.05	21.85	21.90	19.00	54.00	117.00	17.00
3/4″(DN20)	22.00	26.75	25.25	26.30	26.40	24.10	26.58	25.05	25.85	25.90	23.80	63.00	135.00	19.50
1″(DN25)	27.00	33.52	32.25	32.33	34.50	31.00	33.28	32.05	31.85	33.90	30.70	74.00	156.00	23.00
1-1/4″(DN32)	34.00	42.28	40.25	38.43	42.50	39.00	42.05	40.05	37.85	41.90	38.60	85.00	178.00	27.00
1-1/2″(DN40)	42.00	48.40	50.25	48.46	48.60	49.00	48.12	50.05	47.75	47.90	48.60	98.00	205.00	32.00
2″(DN50)	52.00	60.45	63.25	80.56	60.60	61.90	60.18	63.05	59.75	59.90	61.40	118.00	236.00	38.50
2-1/2″(DN65)	67.00	73.30	75.25	76.60	76.70	73.60	72.85	75.05	75.87	75.90	72.30	149.50	277.00	44.50
3″(DN80)	82.00	89.25	90.35	89.60	89.70	88.30	88.70	90.05	88.83	88.90	86.90	72.00	319.00	52.00
4″(DN100)	102.00	114.60	110.35	114.70	115.00	108.00	114.10	110.05	113.98	113.80	106.40	189.00	352.00	62.00

Frequently Asked Questions (FAQs)​

Q1: How does a double union check valve differ from a single check valve?​

A double union check valve provides redundant sealing with two independent check mechanisms, whereas a single check valve has only one, presenting a single point of failure . The double design meets stricter code requirements for low-hazard backflow prevention and includes test ports for compliance verification.

Q2: What maintenance is required for these valves?​

Routine annual testing via test cocks​ is essential to verify both checks hold pressure . Union connections allow internal inspection and seal replacement every 3–5 years, depending on water quality and operating conditions.

Q3: Can double union check valves be installed vertically?​

Yes, most designs accommodate vertical or horizontal installation​ provided flow direction aligns with valve orientation (typically arrow-marked) . Spring-assisted models are recommended for vertical up-flow to ensure swift closure against gravity.

Q4: Are these valves suitable for high-hazard applications?​

No, double union check valves are rated for low-to-medium hazards only​ (fluid categories 2-3) . For high-hazard scenarios (e.g., chemical plants), a reduced pressure zone (RPZ) valve is mandatory due to its advanced fail-safe design.

Q5: How are size and material selected for specific applications?​

Match valve size to pipe diameter​ to avoid excessive pressure drop, and choose materials based on fluid compatibility—bronze for water, stainless steel for chemicals, PVC for irrigation . Pressure and temperature ratings must exceed system operating conditions.