v1 = new Image();
v1.src = '../images/valve1.jpg';
v1_on = new Image();
v1_on.src = '../images/valve1_on.jpg';

v2 = new Image();
v2.src = '../images/valve2.jpg';
v2_on = new Image();
v2_on.src = '../images/valve2_on.jpg';

v3 = new Image();
v3.src = '../images/valve3.jpg';
v3_on = new Image();
v3_on.src = '../images/valve3_on.jpg';

v4 = new Image();
v4.src = '../images/valve4.jpg';
v4_on = new Image();
v4_on.src = '../images/valve4_on.jpg';

v5 = new Image();
v5.src = '../images/valve5.jpg';
v5_on = new Image();
v5_on.src = '../images/valve5_on.jpg';

v6 = new Image();
v6.src = '../images/valve6.jpg';
v6_on = new Image();
v6_on.src = '../images/valve6_on.jpg';

v7 = new Image();
v7.src = '../images/valve7.jpg';
v7_on = new Image();
v7_on.src = '../images/valve7_on.jpg';

v8 = new Image();
v8.src = '../images/valve8.jpg';
v8_on = new Image();
v8_on.src = '../images/valve8_on.jpg';

function navRoll(nav, new_class) {
  document.getElementById(nav).className = new_class;
}