In this brief note, we have experimentally measured the temperature stratification in a solar hot water storage tank resulting from a simulated solar heating load. Various modifications using a double chimney device that acts as a thermal diode were examined with the intent of maximizing temperature stratification. The greatest stratification was seen with a unique thermal diode arrangement named the express-elevator design, so-called for the direct hot water path from the bottom third of the tank to the top third. (C) 2009 Elsevier Ltd. All rights reserved.