I had a girlfriend who's ice maker and refrigerator door water dispense went from under the kitchen sink filter system to the refrigerator via a 1/4" copper tubing. Every time the ice maker called for "water", the copper tubing would jump, causing the owners dog to attack.

But one day the dog was left in the parents kitchen with tile flooring as the family left for a family meeting. The parents had a clear plastic 1/4" water line to provide water to the refrigerator freezer. When that ice maker needed filling, the clean plastic line jumped and the dog attached that line. With the dogs teeth it snapped the plastic line in two. In the next 5 hours the water leak/damage exceeded $100,000. The parents had to move out and it took months to remediate/repair everything.

I plucked the following off of an IFAN website (they sell plumbing supplies):

Case Studies: Real-World Observations

Several case studies have been conducted to observe the interaction between mice and PEX piping. In one study, a household with a history of mouse infestations transitioned from copper to PEX piping. Over a six-month period, there was no reported increase in gnawing activity on the PEX pipes, despite the continued presence of mice in the home. This indicates that PEX piping does not exacerbate rodent problems and may even be less susceptible to damage compared to other materials.

Prevention Measures: Protecting PEX Piping

Although PEX pipes are inherently resistant to mouse chewing, proactive measures can further safeguard the system. Installing PEX pipe in enclosed, inaccessible areas can minimize the risk of gnawing. Additionally, using rodent-proof insulation and barriers around pipes can provide an extra layer of protection. For example, wrapping PEX pipes with steel mesh or rodent-resistant tape can deter even the most determined mice.

Long-Term Durability and Cost-Effectiveness

Never had mouse problems with PEX either.

Squirrel problem in attic once.