Our home has gray plastic water lines. Someone said these lines are likely going to leak. Our home is 30 years old, don’t you think if the lines were going to leak they would have already?

The lines you are talking about are likely poly “B” lines. While it is true these lines have had a poor history and many homes have flooded from this type of pipe, you need to consider a couple of things before you get too excited. As you said, your home is 30 years old and no leaks have developed to this point. The problems with Poly “B” was discovered early on and most of the failures happened in the first couple of years after the pipe was installed. I’m guessing that your poly pipe is fine but just remember to keep an eye on it. The affected poly pipe can be identified by the number PB2110. Even if you have PB2110 in your home you may have no problems if the fittings are copper and they are crimped with copper crimp rings. The majority of the problems with Poly “B” were in the connections between the plastic fittings and the plastic pipe.  visit http://www.polybutylene.com/poly.html  for more information.