Change separators in HTML tags

I’m using WP 4.7.3 and a custom template set (mh-magazine).

By default, WP sets a title tag like “Page title” – “Blog title”.

Now all I want to achieve is to replace “-” into a pipe symbol for layout reasons. So the processed HTMl should look like:

My page title | My blog title

I thought that this is easy to achieve, but I see I need some help since I’m not an expert in PHP or WP.

It all depends on how your theme’s header.php is structured, but the most likely way is via the document_title_separator filter, as in

add_filter ('document_title_separator', 'wpse_set_document_title_separator') ;

function
wpse_set_document_title_separator ($sep)
{
    return ('|') ;
}