how strong is a plastic tubing for a refrigerator line?
It's pretty strong. It must endure water pressure that near 100 PSI, and it also must be able to stand up under the stress of compression fittings.
I pressure tested plastic tubing to failure a few times. Poly tube in 1 ips burst at 400 psi consistently at room temperature. 1/4 cts will burst at a higher pressure, but will fail earlier if exposed to higher temperatures.
