Line Stops

Line stops are temporary or permanent flow control devices that create a complete seal within pressurized water or sewer pipelines without requiring system shutdown or excavation. The system works by inserting an inflatable plug or mechanical stopper through a hot-tap fitting, allowing operators to isolate pipe sections for maintenance, repairs, or tie-ins while maintaining service to other areas. Typical applications handle pressures up to 150 psi in pipes ranging from 4 to 48 inches diameter. The key limitation is that line stops require specialized equipment and certified operators, making them cost-effective only for critical repairs where system shutdown would cause significant service disruption.

• Pipeline Valve Replacement: Line stops enable hot-tap insertion on 6-48" transmission mains to isolate sections for valve replacement without system shutdown. Selected when existing valves fail and isolation would impact service to thousands of customers

• Emergency Repairs: Critical for burst pipe repairs on large diameter (12-36") distribution mains serving multiple pressure zones. Provides temporary isolation while permanent repairs are made

• Tie-In Connections: Used during plant expansions to connect new process piping to existing headers while maintaining plant operations. Common on 8-24" effluent lines and return activated sludge piping

• Meter Installation: Enables insertion of large diameter flow meters (12-30") on existing transmission lines without service interruption. Selected when retrofitting older systems lacking adequate flow measurement for regulatory compliance

Daily Operations: Line stops require minimal daily monitoring once installed. Operators verify valve position indicators and check for visible leaks around completion plugs. Pressure readings upstream and downstream confirm proper sealing. Most installations are temporary, requiring periodic inspection during active construction projects.

​

Maintenance: Permanent installations require annual inspection of valve operation and seal integrity. Maintenance involves confined space entry protocols with gas monitoring and rescue equipment. Requires certified operators with hot-tap training and hydraulic system experience. Valve exercising every 6 months prevents seizing in critical applications.

​

Troubleshooting: Primary failure modes include incomplete pipe penetration and seal leakage around completion plugs. Warning signs include pressure drops, visible water discharge, or inability to fully close insertion valves. Service life typically 20-30 years for permanent installations, though temporary applications may see equipment reused dozens of times across multiple projects.

• Tapping Machine: Hydraulically-powered cutting unit that bores through pipe wall under pressure. Typically rated for 6-48" pipe diameters with carbide-tipped cutters. Selection based on pipe material (ductile iron, steel, PVC) and wall thickness up to 2"

• Completion Plug: Expandable sealing device inserted after tapping to permanently seal the connection. Manufactured from stainless steel or ductile iron with EPDM seals. Sized to match pipe diameter with pressure ratings to 250 PSI

• Hot-Tap Valve: Full-port ball or gate valve assembly that provides isolation capability. Bronze or stainless steel construction for potable water applications. Available in 2-12" sizes with flanged or mechanical joint connections

• Insertion Valve: Resilient-seated gate valve inserted through the tap opening to control flow. Ductile iron body with fusion-bonded epoxy coating. Sized 4-36" diameter with 150-250 PSI pressure ratings for municipal applications

• Pipe Diameter Range: 4" to 72" for municipal applications, with most installations between 8" to 36"

• Operating Pressure: Up to 250 psi working pressure for standard municipal systems; high-pressure versions available to 400 psi for transmission mains

• Wall Thickness Compatibility: Minimum 0.25" for cast iron, 0.375" for steel pipe; maximum penetration depth 2.5" for standard drilling machines

• Flow Velocity Limitations: Maximum 10 fps during installation to prevent drill bit deflection; typical municipal velocities 2-6 fps acceptable

• Pipe Material Requirements: Compatible with ductile iron, cast iron, steel, and AC pipe; not suitable for PVC, HDPE, or concrete pipe without special provisions

• Seal Performance: AWWA C223 compliant seals rated for 50-year service life; operating temperature range -20°F to 180°F

• Installation Clearance: Minimum 18" diameter working space around pipe; 8' minimum overhead clearance for drilling machine setup

• Stopping Plug Materials: Stainless steel or bronze construction; neoprene or EPDM sealing elements rated for potable water contact

• Can the existing pipe wall support drilling loads without structural failure? Requires wall thickness verification, pipe condition assessment, and soil support evaluation. Wrong decision leads to catastrophic pipe failure, flooding, and emergency repairs costing $50,000-200,000

• Is adequate working space available for drilling machine setup and operation? Need minimum 8' x 12' level area with overhead clearance. Insufficient space forces alternative methods like external bypassing, increasing project costs 300-500%

• What is the maximum allowable service interruption duration? Standard line stop installation requires 4-8 hours. Systems serving hospitals, schools, or critical facilities may require hot tapping with temporary bypass, adding $25,000-75,000 to project costs

• Does water quality permit temporary stagnation during installation? High-chlorine residual systems may require pre-flushing procedures. Inadequate planning can cause taste/odor complaints requiring system-wide flushing and customer notifications

• Division 40 - Process Integration

• Section 40 05 23 - Valves for Process Piping Systems

• Primary specification location covering line stop valves, drilling machines, and completion plugs. May cross-reference Division 33 (Utilities) for pipe modifications

• Material/Equipment Verification: Verify pressure rating matches system operating pressure plus safety margin; Confirm fitting material compatibility (ductile iron, steel, PVC); Check gasket material for water quality compatibility

• Installation Requirements: Minimum 18" clearance around pipe for drilling machine setup; Stable work platform or excavation shoring; Power source for drilling equipment (typically 480V)

• Field Challenges: Limited access in congested utility corridors; Pipe deflection under load during drilling; Maintaining sterile conditions during connection

• Coordination Issues: 2-4 week lead time for custom fittings; Utility notification requirements; Traffic control coordination

• Mueller Water Products - StopTite line stopping machines and fittings, dominant in North American municipal market with machines from 4" to 48" diameter

• Smith-Blair - FullPort line stops and drilling machines, strong presence in Southeast utilities

• Team Corporation - LineStop systems and hot tapping equipment, popular for larger diameter applications 24" and above

• Romac Industries - MegaLug line stop fittings and accessories

• Valve insertion using Clow or Mueller machines - preferred for permanent isolation, $8,000-15,000 installed versus $3,000-8,000 for temporary line stops

• Freeze stopping using liquid nitrogen - ideal for emergency repairs on small diameter lines under 12", $2,000-5,000 per application but limited duration

• Bypass pumping - necessary for critical mains where flow interruption isn't acceptable, $5,000-20,000 depending on capacity and duration

Always order backup gaskets and verify actual pipe outside diameter before fabrication - many older systems have non-standard dimensions. Establish relationships with regional Mueller or Smith-Blair distributors for emergency equipment rental. Consider renting drilling machines rather than purchasing for infrequent use - typical rental costs $500-800/day versus $15,000-40,000 purchase price depending on size.