When purchasing pipes, pay attention to their appearance: the pipes should be smooth, as inside and out. If there are minor irregularities on the pipe, waves, this is also not a deviation from the norms. The main thing is that there are no significant chips, cracks that violate the integrity, interspersed of foreign materials. Most often PND pipes are painted black, stripes marking the pipe are applied blue. In addition, if you plan to use water from the water supply for drinking, you need to clarify when buying so that the pipe is made of material that can be used for drinking water.
