Many people often only focus on the price and diameter of PVC pipes when arranging outdoor drainage systems, but ignore the two major "invisible damages" of the outdoor environment - low temperature freezing in winter and UV exposure in summer. If you choose the wrong pipe, it will not take a few years to crack, leak, age and become brittle. Rework and maintenance are both expensive and troublesome. Today, let's explain the core points of PVC outdoor drainage pipe selection: how to judge the anti-freezing performance, how to choose the sunscreen material, and how to match the specifications, to help you choose the right durable pipe in one step.

Let's talk about anti-freezing first - in the winter in the north, low temperature is the "natural enemy" of PVC pipes. Ordinary PVC pipes will lose their toughness when they are cold and become "brittle". Once they encounter freezing and expansion (such as water freezing in the pipe) or soil extrusion, they can easily crack into "spider webs". To choose an impact-resistant modified PVC-U pipe, ACR (acrylate copolymer) or CPE (chlorinated polyethylene) are added to this pipe, which can greatly improve the low-temperature toughness. How to choose? See the "Low-temperature drop hammer impact test" in the product test report: If you can pass -20 ° C (or even lower) impact on the pipe that does not break, the frost resistance will pass the test. In addition, the wall thickness is also critical - the thicker the wall thickness of the PVC pipe of the same specification (for example, the S2 grade is thicker than the S3.2 grade), the stronger the frost resistance and impact resistance. If it is a drain pipe installed in the north (such as a rain pipe outside the balcony), be sure to choose a high frost resistance grade; if it is buried, remember to bury it below the local permafrost layer (such as Beijing permafrost layer is about 0.8 meters), double protection.

Let's talk about sun protection again - the ultraviolet rays in the south are no joke, ordinary PVC pipes will "slowly age" after long-term exposure to the sun: the surface changes from smooth to rough, the color changes from dark to light, the internal structure is damaged by ultraviolet rays, and the toughness is getting worse and worse. After three or five years, it will be broken with a light knock. Choose a tube with anti-ultraviolet stabilizer, such as one containing carbon black or ultraviolet absorber. You can quickly tell from the appearance: black or dark gray PVC pipes are better than white and light-colored sunscreens - because carbon black is a natural UV "shield" that blocks most of the ultraviolet rays outside. Some merchants say that "white pipes have sunscreen added," but in actual use, dark pipes have more reliable sun protection stability. If it is an external wall rain pipe installed on the surface, choose black or dark gray first; if you have already bought a light-colored pipe, remember to wrap a layer of sunscreen insulation tape, but it is still better to choose the right pipe to save worry.

Finally, the specifications match - choose the right size and strength to ensure that the drainage is "smooth and smooth". First look at the pipe diameter: DN50 (inner diameter 50mm) is enough for kitchen sink and washing machine drainage; DN75 or DN100 should be used for toilets (toilets + wash basins); outdoor rain pipes should be calculated according to the roof area: for every 100 square meters of roof, choose DN100 pipes (about 15 cubic meters of displacement per hour); villas can choose DN150 for large roofs. Then look at the ring stiffness (external pressure resistance): buried pipes must choose SN8 (ring stiffness 8kN/m2), because the soil will be under pressure, especially in areas where vehicles are rolling, SN8 can handle it; surface-mounted pipes should choose SN4, but for high-rise external walls, SN8 is recommended to be stronger. There is also a connection method. PVC drain pipes are generally bonded with sockets. Pipe fittings of the same brand and specification should be selected. Wipe the interface clean before sticking, and use special glue to avoid water leakage.

In fact, the selection logic of PVC outdoor drain pipes is very simple: the region determines the focus (north frost resistance, south sun protection), the environment determines the details (surface installation/buried ground selection strength), and the demand determines the specification (discharge selection pipe diameter). If you choose the right one, you don't have to worry about it for 20 or 30 years; if you choose the wrong one, it will be troublesome to repair the pipe every year. When choosing a pipe next time, don't just look at the price, but figure out the three points of antifreeze, sun protection and specifications to choose a really durable pipe.