How to share repeated fields across multiple pages?

The ACF functions accept a second argument which is the ID of the page you wish to retrieve the fields from. See the code examples in documentation.

$page_id = 120;
if( get_field( 'treatments', $page_id ) ):

    while( has_sub_field( 'treatments', $page_id ) ):

        // the_sub_field and get_sub_field don't need a post id parameter
        the_sub_field('image' );
        the_sub_field('description' );

    endwhile;

endif;