Pex pipe predicament.

[Bszweda]

Water lines going to ice makers and dish washers gives me anxiety. A dollar plastic fitting or pipe failing and causing thousands of dollars in water damage. Found this from Google an odd diameter is European
A ".511 diameter dishwasher pipe" generally refers to a drain hose with an internal diameter (ID) of approximately 13mm (0.51 inches). This specific size is commonly found in European-style dishwasher drain hoses or, in some cases, might be referred to as 1/2-inch or 5/8-inch in universal, trimmable kits.

That being said after looking at the picture I agree with Jerry that the pex pipe likely swelled.

 

[Telemark]

Water lines going to ice makers and dish washers gives me anxiety

You can get a valve and alarm unit that will shut off the water and beep like crazy. We have one under the fridge. It's basically a cord with insulation removed in spots that shorts when it comes into contact with water. It won't clean up the mess, but it will prevent it from becoming catastrophic and alert you to the problem. If someone kicks an ice cube under the fridge, that can set it off, which is a huge pain in the butt. You get to drag the whole thing out and clean all the dust from under the fridge and then carefully put the cord back.

 

[Jerry-B-WI]

That tubing could be 13mm.
.511811 inch is 13 mm

We had metric tubing at work for some of our robots. Stuff was a PITA to match up fittings.

 

[MadMadHoosier]

You can get a valve and alarm unit that will shut off the water and beep like crazy. We have one under the fridge. It's basically a cord with insulation removed in spots that shorts when it comes into contact with water. It won't clean up the mess, but it will prevent it from becoming catastrophic and alert you to the problem. If someone kicks an ice cube under the fridge, that can set it off, which is a huge pain in the butt. You get to drag the whole thing out and clean all the dust from under the fridge and then carefully put the cord back.

We tried a few under counter leak detectors, but did not like keeping up with batteries and how many were necessary for every sink, water heater, dish washer, washing machine, etc. so we went the whole house route.

This Flo by Moen smart water valve learns how you use water and alerts you to any anomalies and can even automatically shut the water off for suspicious usage (leaks) if you want it to.

A little pricey, but the insurance company gave us a discount on our homeowners insurance that helps a bit - so they believe in them. It helped us find a toilet that had a trickle leak we probably never would have found otherwise. We liked it so much we also installed one at the farm cabin. It's really nice using the app to check water pressure and turn the water off/on as we come and go to the cabin.

 

[Telemark]

We tried a few under counter leak detectors, but did not like keeping up with batteries and how many were necessary for every sink, water heater, dish washer, washing machine, etc. so we went the whole house route.

Ours plugs into the wall.