Tilting Disc Check Valves

Tilting disc check valves prevent reverse flow in municipal water and wastewater systems by using a hinged disc that opens under forward flow pressure and closes when flow stops or reverses. The disc tilts at an angle rather than lifting straight up, creating a streamlined flow path with minimal pressure drop. These valves typically achieve cracking pressures as low as 0.02-0.05 psi, making them ideal for low-head applications like gravity discharge lines and pump station force mains. The primary trade-off is their susceptibility to disc flutter and potential slam closure during rapid flow reversals, which can cause water hammer in larger diameter applications above 24 inches.

• Raw Water Intake Pumps (2-48" diameter): Installed downstream of vertical turbine pumps at intake structures, preventing reverse flow during pump shutdown. Selected for minimal head loss (0.5-2 psi) and ability to handle debris-laden raw water
• High Service Pump Discharge (6-36" diameter): Mounted on finished water pump discharge lines before distribution headers. Chosen for fast closure (0.5-2 seconds) to prevent water hammer and maintain system pressure during pump cycling
• Backwash Water Supply (8-24" diameter): Protects backwash pumps from filter gallery pressure surges during rapid startup/shutdown cycles. Selected for tight shutoff and low cracking pressure (1-3 psi)
• Clearwell Outlet Lines (12-48" diameter): Prevents gravity flow reversal when multiple clearwells operate at different levels, maintaining disinfection contact time compliance per CT requirements

Daily Operations: Operators monitor pump station flow meters and pressure gauges to verify proper valve operation during pump starts/stops. No adjustments required during normal operation. Visual inspection of external counterweights (if equipped) for proper positioning. Listen for unusual noise during pump cycling indicating potential disc flutter or seat damage.

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Maintenance: Annual internal inspection during scheduled pump maintenance outages. Requires confined space entry procedures and fall protection for large diameter installations. Lubricate trunnion bearings every 6 months using food-grade grease. Replace seat rings every 10-15 years or when leakage exceeds 1% of design flow. Maintenance requires millwright skills for disc removal and seat replacement.

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Troubleshooting: Water hammer indicates slow closure - check spring tension or counterweight adjustment. Continuous reverse flow suggests seat damage or debris lodged in disc. Chattering during low flow indicates undersized valve or inadequate closure force. Typical service life 20-25 years with proper maintenance. Replace when seat leakage exceeds 5% design flow or disc shows cracking.

• Tilting Disc Assembly: Cast iron or ductile iron disc (6-48" typical municipal range) pivots on trunnion pins, opening at 15-30° angle. Disc thickness varies 1-4" based on pressure class. Selection factors include flow velocity limits (8-12 fps) and pressure rating (125-250 psi standard)
• Body/Seat Ring: Cast iron or ductile iron body with integral or replaceable seat ring. Seat materials include EPDM, Buna-N, or metal-to-metal for high-temperature service. Size selection based on pipe diameter and pressure class requirements
• Spring/Counterweight System: Provides closure assistance and prevents disc flutter. Stainless steel springs or external counterweights sized for specific gravity and flow conditions. Critical for preventing premature wear in variable flow applications
• Trunnion Bearings: Bronze or stainless steel bushings support disc rotation. Require periodic lubrication and replacement every 8-12 years depending on water quality and cycling frequency

• Flow Velocity Requirements: Minimum opening velocity: 2-3 fps (prevents chatter and incomplete seating), Maximum velocity: 15 fps (prevents excessive wear and water hammer), Optimal operating range: 4-8 fps for municipal applications
• Pressure Parameters: Working pressure: 150-300 psi (ANSI Class 150/300 standard), Minimum cracking pressure: 0.1-0.5 psi (varies by size and spring loading), Maximum allowable backpressure: Equal to working pressure rating
• Sizing Guidelines: Pipe sizes: 4" through 48" diameter (municipal range), Flow rates: 200 GPM (6" valve) to 15,000 GPM (36" valve), Cv values: 150-12,000 (size dependent)
• Head Loss Characteristics: Fully open head loss: 0.5-2.0 feet at design flow, Head loss coefficient (K): 0.5-1.5 depending on disc design, Spring-loaded models add 0.2-0.8 feet additional loss
• Material Specifications: Body: Ductile iron (ASTM A536), stainless steel (316SS for aggressive service), Disc/seat: EPDM, Buna-N, or metal-to-metal for high-temperature applications, Temperature range: 32-180°F (standard elastomers)

• What is the minimum sustained flow rate, and does it exceed 2-3 fps valve velocity? Engineers must verify minimum flow maintains adequate disc positioning. Below 2 fps, discs flutter and create premature wear. Calculate using Q(GPM) = 2.45 × d² × V(fps). Consequence: Valve chatter reduces service life from 20+ years to 3-5 years
• Will the valve experience reverse flow conditions exceeding 50% of forward design flow? High reverse velocities (>8 fps) cause slam-shut conditions and potential disc damage. Evaluate pump trip scenarios and gravity flow reversals. Consequence: Disc warping or seat damage requires costly replacement and system downtime
• Does the application require spring-assisted closure for low-flow conditions? Standard tilting disc valves may not fully close below 1 fps reverse flow. Spring-loaded versions ensure tight shutoff but increase head loss by 0.2-0.8 feet. Consequence: Improper selection causes backflow during low-pressure periods or excessive pumping costs
• What are the water quality parameters, particularly suspended solids and aggressive chemicals? TSS >50 mg/L or chlorine >2 ppm may require upgraded seat materials or frequent maintenance. Standard EPDM seats degrade rapidly in high-chlorine environments

• Material/Equipment Verification: Verify disc material compatibility with local water chemistry, Confirm seat material meets NSF/ANSI 61 requirements, Check spring material for chlorine resistance
• Installation Requirements: Minimum 10D straight pipe upstream recommended, Access space for maintenance above valve, Proper thrust restraint design critical
• Field Challenges: Alignment sensitivity during installation, Torque specifications vary by manufacturer, Lead times typically 8-12 weeks for municipal sizes
• Coordination Issues: Coordinate with structural for valve vault sizing, Electrical coordination if position indication required

• Apco - Model 400 series tilting disc valves, strong municipal presence with 4"-48" sizes
• Val-Matic - Model 210 series, popular for pump station applications 6"-60"
• Cla-Val - CV-6 series, reliable for water distribution 4"-36"
• Mueller Water Products - Resilient seated models, competitive pricing for standard municipal applications

• Swing Check Valves - Lower cost, better for low-flow applications, 20-30% cheaper but larger footprint
• Ball Check Valves - Superior sealing, preferred for high-pressure applications, 40-50% higher cost
• Duckbill Valves - Excellent for gravity applications, significantly lower cost but limited to low-pressure scenarios under 25 psi

Establish relationships with local manufacturer reps early - they provide valuable technical support during commissioning. Consider standardizing on one manufacturer across facilities to reduce spare parts inventory. Negotiate volume pricing for multiple installations. Always specify internal inspection ports on larger valves (>24") - saves significant maintenance costs versus complete removal for inspection.