I am helping to create a website for a human rights organization in Angola. They use BuddyPress for having members overview and bbPress for the forums. I added a private forum link in the menu so that when the user signs in they have easy access to it. That also meant that I had to redirect not logged in users.

To hide all BuddyPress pages so that they do not happen to become visible for non logged in users I used this code that I added to the child theme functions.php file.

// Protect BuddyPress pages and bbPress forums: Not logged in users get redirected to an information page.
function ps_guest_redirect() {
     global $bp;
  if ( is_buddypress() || bp_is_user() || is_bbpress() ) {
      if(!is_user_logged_in()) {
           wp_redirect(' https://direitoshumanosangola.org/not-logged-in/');
  exit;
      }
  }
}
add_filter('get_header','ps_guest_redirect',1);

The above code:
If it is buddypress or bp user or is bbpress and user is not logged inn then redirect to a not logged in page.

Code where BuddyPress redirects to one page and bbPress redirects to another page.

function ps_guest_redirect() {
   global $bp;
   if ( is_buddypress() || bp_is_user() ) {
     if(!is_user_logged_in()) {
      wp_redirect('https://direitoshumanosangola.org/not-logged-in/');
   exit;
      }
  }
  if(is_bbpress()){
     if(!is_user_logged_in()) {
     wp_redirect('https://direitoshumanosangola.org/');
  exit;
     }
  }
}
add_filter('get_header','ps_guest_redirect',1);

The problem with the above code is that bbPress private forums will give a 404 error code and not redirect. To also redirect a private bbPress forum use the following code:

// Redirect private bbPress forum to specific page.
add_action('template_redirect', 'private_content_redirect_to_login', 9);
function private_content_redirect_to_login() {
    global $wp_query,$wpdb;
    if (is_404() and !is_user_logged_in()) {
      $host = $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
      $path = dirname($_SERVER['REQUEST_URI']);
      $forums = "forum";
      $location = "https://direitoshumanosangola.org/not-logged-in/";
      }
      if(strpos( $path, $forums ) !== false){
        wp_safe_redirect($location);
        exit;
    }
}

The only thing you need to adjust is the $location url. It should then work nicely.

NB! Remember to clear your cache to see the changes.

Resources:
The BuddyPress Slack channel. A huge thank you to Prashant for helping me with the code!
wordpress.slack.com/archives/C02RQBYUG/p1538777140000100

stackoverflow.com/questions/47196124/bbpress-private-forum-redirect-to-login
seventhqueen.com/blog/code-snippets/restrict-guest-users-from-accessing-buddypress-or-bbpress-pages.html