The house was constructed with a valve & a water line extending through the foundation to service water when a barn was built . The barn is now completed and is 430 feet from the house about a ten foot rise in elevation. The pipe extending from the house is cresline 1 inch plastic tubing. Should I use the same materials to extend the line to the barn or reduce the size 3/4 or 1/2 inch ? Use a different material ? Considerations are ease & cost. The line will be buried 36 inches.

Don't go smaller. With friction loss at that distance you won't get much flow.
PVC or PE pipe would work. I will assume this is PVC.

Hi Doug

To determine pipe size, we would need to know exactly what you'll plan on needing water for... fixtures, outside faucets, filling troughs... what?

Like Ma0641 said, you definitely will not reduce pipe size, for sure. Stick with the black cresline polyethylene piping for underground... can't go wrong using that!

Back to you...

Mark