Those annoying cold patches are called the "Sandwich Effect" . A term I fist heard when I talked to the plumber who installed the gas tankless in our home, about three years ago. I am still here because this technology will be better able to handle that common problem. We have cold well water....not 55 degree city water. To make it more robust and like the old tank style we had a 1 gal tank installed in the loop with the gas unit and it constantly keeps that 1 gal at 130. Helps the problem but kills the energy efficiency IMO. Faster conversion will save water wasted waiting for heat also.... I posted this link before, .... credit here to Tani.... its an old article that touted our heater for 2010.( LOL) Potential is huge worldwide if/when the mfg starts. Go Robert, Bruno, and Dave!!!! You guys kept me here. http://joneakes.com/cgi-bin/getdetailscals.cgi?id=1947