How to correctly install the inlet and outlet pipes of the fan coil unit and avoid water leakage?

The installation quality of cooling tower piping directly impacts operational safety. 37% of air conditioner leakage failures are caused by improper installation. Applying scientific installation procedures can effectively prevent ceiling leaks, equipment damage, and other malfunctions. The following core tutorial examines detailed leak-proof considerations.

Material Selection: Building Leak-Proof Foundations
Hot water systems should utilize hot-dip galvanized steel pipes (DN≤100mm) or PP-R pipes (temperature tolerance ≤70℃). Cold water systems may use galvanized steel pipes or PE-RT pipes. Employ 45° or 90° elbow press fittings with curvature radius ≥1.5D. Bronze valves must have pressure ratings ≥1.6MPa, with EPDM seals for hot water and NBR for cold water.

For steel pipe connections:

1. Wrap PTFE tape clockwise (5-7 layers)
2. Apply thread sealant
   PP-R hot fusion temperature: 260±10℃. Welding duration: 6 seconds for DN25 pipes. Install rubber flexible joints (working pressure ≥1.0MPa) 150-300mm from coil connections. Terminate with fixed supports.

Standard Installation: Core Leak Prevention
Pipe routing: Adopt “top-supply/bottom-return” or “bottom-supply/bottom-return” layouts. Minimum slopes:

• 0.003 for metal pipes
• 0.01 for composite pipes
  Support spacing:
• ≤3m for DN25 steel pipes
• ≤1.5m for PP-R pipes
  Use 3mm steel spacers between supports and pipes.

Welding specifications:

• Steel pipe crown welding with subsequent kerosene penetration testing
• Allow natural cooling for PP-R (5 minutes for DN25)
  Pressure testing:
• Cold systems: 0.6MPa for 30 min → max drop 0.02MPa
• Hot systems: 1.0MPa for 60 min → max drop 0.05MPa

Detailing: Eliminating Connection Leaks
Insulation requirements:

• Closed-cell rubber foam ≥20mm (for DN≤50 pipes)
• Apply specialty adhesive at joints
• Seal with aluminum foil tape

Install 50mm water seals at protective pipes. Branch-main connections: 45° angle. Terminate with tented caps. Critical components:

• Y-strainers (≥20 mesh) ≥5 pipe diameters from coil inlets
• Balancing valves on return lines
• Bronze ball valves at all coil connections
• Valves (≥DN20) at manifolds
• Manual air vents at system high points

Leak Repair & Maintenance: Long-Term Prevention
Leak diagnosis:

• Inspect PTFE tape application techniques
• Verify PP-R fusion bead formation (1-2mm)
  Emergency repair:
• Apply waterproof tape
• Install clamp-on rubber pads with stoppers
• Close upstream valves

Inspection protocols:

• Verify slopes with levels (±0.001 tolerance)
• Clean filter screens quarterly
• Annual hydrostatic retesting
• Replace flexible joints periodically
• Conduct condensate line tests using piping inspection balls (diameter ≥0.7 pipe diameter)

Implementing these material, installation, detailing, and maintenance procedures significantly reduces leakage risks. Translating them into operational protocols ensures long-term reliability of fan coil unit piping systems.