I am about to relocate my F&E tank and on closer inspection I find that the existing tank has a combined feed, expansion and vent. That is to say there is a single 22mm/3/4" outlet from tank that Tees directly to a 15mm vent, the feed and expansion pipe is 22mm. Question is should I take the considerable trouble to run a new seperate vent when installing the new tank or would it be acceptable to retain the existing arrangement. Its worth noting that I have not had any problems with the existing set up. Thanks.