Polypropylene pipes (PP pipes) are widely used in water supply and drainage, HVAC, and chemical industries due to their corrosion resistance, high temperature resistance, and long lifespan. However, improper installation or maintenance can lead to leaks, deformation, or even system failure. The following key techniques, from selection and installation to maintenance, will help you use polypropylene pipes efficiently.
Selection: Matching the Scenario is Fundamental
Polypropylene pipes are classified by material into homopolymer PP (such as PP-H) and copolymer PP (such as PP-B and PP-R). PP-R (random copolymer polypropylene) has the best overall performance, with high temperature resistance (long-term operating temperature up to 70℃) and strong impact resistance, making it suitable for household hot water pipes and HVAC systems; PP-B has good impact resistance but slightly weaker high temperature resistance, and is mostly used for cold water pipes; PP-H has high rigidity but poor flexibility, and is often used for industrial corrosion-resistant fluid transportation. When selecting a pipe, it is necessary to specify the medium (water/chemical agents), temperature (long-term maximum temperature), and pressure rating (commonly PN1.0-2.5MPa) to avoid under-fitting the system.
Installation: Details Determine Success or Failure
1. Pre-treatment and Cutting
Before installation, clean the pipes and joints of oil and burrs to ensure a smooth surface. For cutting, it is recommended to use a dedicated PP pipe cutter or a fine-toothed hacksaw. The cut must be vertical and flat (deviation ≤ 0.5°), otherwise it will affect the weld seal. If the cut is uneven, it can be smoothed with a file or sandpaper.
2. Welding Process (Hot Fusion Connection as the Core)
PP pipes are mainly connected by hot fusion (socket type). The key parameters are temperature and time: The hot fusion temperature of PP-R pipes is usually 260±10℃ (slightly different for different brands; refer to the instruction manual). During operation:
• First, insert both the fitting and the pipe into the heat fusion machine to the specified depth (e.g., approximately 14mm for a Φ20mm pipe), heating for about 5-7 seconds (longer for larger pipe diameters);
• Immediately after heating, insert the pipe into the fitting at a uniform speed to the marked depth (do not rotate!), maintain pressure for 2-3 seconds until cooling (cooling time is approximately 30-60 seconds, during which time movement is prohibited);
• If "bulges" or "gaps" appear after welding, it indicates overheating or incomplete insertion, requiring sawing and re-welding.
3. Supports and Spacing
Pipes must be fixed with dedicated plastic supports (do not allow direct contact with metal supports to avoid electrochemical corrosion). For horizontal pipes, install one support every 2-3 meters; for vertical pipes, at least one fixing point per floor. At bends (e.g., 90° elbows), additional supports must be installed within 200mm on both sides to prevent stress concentration and joint cracking.
4. Special Considerations for Certain Scenarios
• Exposed Pipes: It is recommended to install an insulation layer (such as rubber-plastic sponge) to avoid direct sunlight accelerating aging (UV rays can make the PP pipe surface brittle);
• Buried Pipes: The bottom of the pipe trench must be compacted and covered with fine sand (thickness ≥100mm). When backfilling, first fill with soft soil and then gradually compact it to avoid hard objects damaging the pipe;
• Connections with Metal Components: Transition joints (such as PP-R flanges + stainless steel bolts) are required to prevent potential difference corrosion.
Maintenance: The Key to Extending Lifespan
1. Daily Inspection: Regularly observe the pipe surface for cracks, deformation, or water stains (especially at joints), and listen for abnormal water flow sounds (which may indicate minor leaks). In low-temperature areas during winter (below 5℃), drain any accumulated water from the pipes or wrap them with insulation material to prevent the PP pipes from becoming brittle and cracking at low temperatures.
2. Cleaning and Anti-Clogging: Avoid pouring grease or chemicals (such as strong acids/alkalis) into the pipes. After long-term use, use a 5% citric acid solution for circulating cleaning (water temperature ≤60℃) to remove scale. If a blockage occurs, use a drain cleaner for physical cleaning first; never use a steel wool pad to scrape (it will scratch the inner wall).
3. Aging Treatment Under normal use, PP pipes can last up to 50 years. However, if they become noticeably brittle, discolored (e.g., yellowing), or leak frequently at the joints, it is recommended to replace them partially rather than repair them (heat fusion repair may affect the overall strength).
Mastering these techniques will allow polypropylene pipes to not only leverage their advantages of corrosion resistance and long lifespan but also avoid common installation problems, making the piping system safer and more reliable.
