Updated InterNACHI Gallery graphic of the expansion tanks for the boiler system

We updated graphics of the expansion tanks inside InterNACHI’s free, online “How to Inspect HVAC Systems” course at http://education.nachi.org/show.php?course_id=65&element_id=1619.

InterNACHI’s Gallery illustration has also been updated at http://www.nachi.org/gallery/hvac/heating/expansion-tank-water-levels-boiler-internachi.jpg.