During the operation of underfloor heating systems, if PE-RT pipes in exposed areas are damaged due to construction impacts or later modifications, they can be partially repaired through hot-melt process thanks to their thermoplastic material properties, without replacing the entire pipe. This is also the core operational advantage of PE-RT compared to PEX cross-linked pipes.
I. Repair Prerequisites: Only Applicable to Thermoplastic Pipes
Hot-melt repair melts the pipe end face by heating and fuses it with the same material fitting into one body. It is only applicable to thermoplastic non-crosslinked pipes such as PE-RT, conforming to GB/T 28799 standard requirements. PEX cross-linked pipes have a network molecular structure and cannot be remelted and bonded after heating, so they can only be replaced entirely after damage. Even for PE-RT, repairs are limited to exposed areas above ground that are accessible for inspection.
II. Standard Process: Five Standard Operation Steps
1. Preprocessing: Locate the damage point, cut out the pipe section (leave ≥10cm healthy pipe at both ends), make the cut perpendicular to remove burrs, clean and dry.
2. Preparation: Same specification PE-RT straight coupling + dedicated hot-melt device (240~260°C), mark insertion depth on pipe end to prevent diameter reduction. Construction environment should be ≥5°C.
3. Synchronous Heating: Push pipe end and fitting socket into heating mold simultaneously, keep coaxial without rotation. DN20 approx. 8 sec / DN25 approx. 10 sec (<5°C extend by 50%).
4. Butt Joint Curing: After reaching heating time, quickly remove and insert vertically to marked depth, forming a uniform ring flange; natural cooling, prohibit twisting or applying force during cooling.
5. Pressure Test Verification: 0.6MPa stable pressure for 1h, pressure drop ≤0.05MPa is qualified; proceed to next process under maintained pressure.
III. Acceptance Criteria: Three Core Dimensions
1. Visual Inspection: Joint concentric without tilt, external melt bead uniform and continuous, no obvious melt accumulation inside, avoiding diameter reduction affecting water flow.
2. Pressure Acceptance: Strictly implement pressure test process, pressure drop exceeding standard must rework and reconnect, prohibit direct concealment without pressure test.
3. Location Record: Exposed joints should be marked on as-built drawings and kept on record for future maintenance.
IV. Common Misconceptions: Five Types of Operations to Avoid
1. Mixing Fittings: Using PPR couplings instead of PE-RT dedicated fittings, material melting point and molecular structure differ, insufficient welding strength, prone to separation and leakage later.
2. Temperature Out of Control: Too high causes PE material degradation and aging, reducing joint strength; too low results in insufficient fusion, seal failure.
3. Rotating During Insertion: Rotation destroys the molten bonding surface, forming false weld gaps, leaving long-term leakage hazards.
4. Shortening Cooling Time: Moving before fully cured causes joint misalignment and strength reduction.
5. ❌ Buried Joint: After concrete solidification in the fill layer, joints bear thermal expansion/contraction stress and ground load and are completely inaccessible for inspection. Once leakage occurs, the floor must be broken open, with repair costs over 100 times that of standard construction. The only correct approach for buried area damage is to replace the entire loop.
The thermoplastic properties of PE-RT make maintenance in exposed areas efficient and convenient, greatly reducing operation and maintenance costs. However, repair quality highly depends on operation standards, and must be strictly limited to inspectable exposed areas. Following process standards and industry norms can truly leverage material advantages and ensure long-term reliable operation of the system.
