decoration or water and electricity renovation, many people will encounter such confusion: the PPR pipe originally used in the home, want to connect the new cloth PE pipe, can it be directly hot-melted or plugged? The answer is actually very clear - PPR pipe and PE pipe can not be directly connected, the reason behind the hidden in the material characteristics and connection principle of the two pipes.

First clarify the basics: PPR pipe is random copolymer polypropylene, strong rigidity, high temperature resistance (long-term use can carry 70 ℃), hot melt connection requires a high temperature of 190-240 ℃; PE pipe is polyethylene, good flexibility, low temperature resistance, but the hot melt temperature is only 140-180 ℃. The difference in hot melt temperature between the two is more than 50 ° C. If the direct hot melt is forced, either the PPR pipe has not been fully melted (the interface is not firmly adhered), or the PE pipe has been over-melted (turned into a sticky "thinner"), and a tight sealing layer cannot be formed at all.

is more critical because the material shrinkage rate is different: the shrinkage rate of PPR is about 0.5%, and that of PE is 1.5% -3%. Even if it is barely connected, the stress at the interface will continue to accumulate when the heat expands and contracts later - when it heats up in summer, the PE pipe expands more obviously, which will "loosen" the PPR interface; when it cools down in winter, the PE pipe shrinks faster and directly cracks the interface. It won't take long for water to leak, and even if the whole pipe is disengaged and buried in the wall or underground, the maintenance cost is extremely high.

What are the correct connection methods? These 3 are commonly used in the industry:

1. Hot melt adapter (most recommended): buy one end is PPR, one end is PE "conversion pipe fittings" (such as PPR-PE direct head, elbow), respectively, with the corresponding temperature hot melt - PPR end with PPR hot melt machine (about 200 ℃), PE end with PE hot melt machine (about 160 ℃). This method has the best sealing effect and also conforms to the specifications of pipeline engineering.

2. Mechanical connection (suitable for old pipe transformation): If it is already fixed pipeline, can not use hot melt machine, you can choose clamp type or threaded mechanical joint. For example, use a clamp with a sealing ring to clamp the PPR and PE pipes tightly, or add threaded joints at both ends (PPR end wire, PE end wire), and then use a live connection. The disadvantage is that the interface is large in size, but it is more flexible.

3. Electrofusion connection (special for large pipe diameter): For PE pipes with a diameter of more than 63mm (such as outdoor water supply), the pipe can be converted by electrofusion - there is a resistance wire on the inner wall of the pipe. After power on, the resistance heats and melts the interface, so that the PPR and PE pipe can be fused. This method requires special equipment, but the connection strength is higher than that of hot melt.

Finally, remind 3 points of precautions: ① No matter which method is used, the pipe fittings must be selected in line with the national standard (GB/T 18742 or GB/T 13663), and do not buy "three no" products; ② When hot melting, you must "plug in and pull slowly" to ensure that there is no gap at the interface; ③ After connecting, you must do "stress testing" - use a pressure test pump to hit 8-10 kg of pressure and keep the pressure for 30 minutes without falling off.

In fact, PPR and PE pipes are good materials, but "there are specializations in the industry": PPR is suitable for indoor hot water pipes and water supply pipes, and PE is suitable for outdoor cold water and buried pipes. As long as you use the right connection method, you can fully play the advantages of both. Don't try to save trouble and connect directly, otherwise a leak of water will be enough to buy 10 adapters.

sum up: PPR and PE pipes cannot be directly touched, but with the right "bridge" (conversion pipe fittings), they can be safely connected. When decorating, ask the master "Is the adapter used?", which is more useful than the leak repair pipe afterwards.