The reason for the bulging of the plastic water pipe in the bathroom

Frost cracking --- without heating in winter is also possible, but installation or quality is more likely.

There are many reasons for the burst:

Before or during installation, the pipe is subjected to external force, which causes the pipe to crack invisibly and burst under pressure;

Instantaneous excessive pressure in the pipe, or water hammer effect to the point of bursting the pipe (1st or 2nd floor);

The specifications of the use series are improper, and the wall thickness series is low, which cannot meet the requirements of use;

The temperature at the pipe is too low, and the ice will burst the pipe;

The quality of the pipe itself, impurity points, local wall thickness is thin, concave points, etc.

Now the manufacturers of cold water pipes are adding recycled materials to reduce costs, and the temperature drops in winter, and the aging compressive strength of the pipe is low, and it naturally explodes.

It's a matter of quality, you can find a supplier.