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The leak is most likely in a fitting and not the line itself, unless this is one that has the old CPVC lines and then those can be hard to spot. That is the hard yellowish line. The newer lines are gray Pex or similar. So check the fittings for being loose or cracked. If you can attach a photo of the area that is leaking (or where you suspect it) that would help. If this is near the water heater, the tank may have a pinhole lead and is seeping. Hope that helps here. I will also make a phone chat option available for you in case you think that might be more productive.
Just checking back to see if you were able to resolve this issue with the material I provided or do you still need some additional input from me here?