Know where 7.1 sanatizes the domain address?

I would like to know where it is stripping off the 'www' off the web address.  

I found a function called getDomain but it's under the Sites Module so that's not it because what if you don't load that module?

Appreciate any directional pointing on this.

 In your site root /inc/header.inc.php

add the www there.

Look at line 21,22 and change line 23

$site['ver']               = '7.1';

$site['build']             = '4';

$site['url']               = "http://www.yoursite.com/";

Sweet. Thanks. So obvious I overlooked it.