Can PVC Pipe be used in attics as a water supply line? Even if it is insulated?
IRC and UPC indicates that PVC Plastic Pipe is OK for service, just not for distribution.
Are you perhaps refering to CPVC and not PVC?
PVC is allowed for cold water distribution outside of the building. If it's insulated, I'd bet that it's being used for hot water distribution.
CPVC (as Michael mentioned) can be used for hot and cold.
I see PVC used for service entry all the time. As for Hot/Cold distribution, we normally see CPVC or Copper in our neck of the woods.
What I don't see, is insulation on service or distribution lines, on any kind of regular basis. I always recommend to my clients to consider insulating these lines as an energy conserving addition to the system.
I believe that pvc is rated up to about 140 degrees (CPVC-180), I don't know about New Mexico but here in Florida I have seen attics over 140.
In Iowa I plumbed under the UPC and PVC or CPVC was illegal to use. PVC expands and contracts quite a bit so I sure would not want to use it for any water under preasure (even Schedule 80) and certainly not in cold climates.