This has been a very interesting thread for me as it has made me stop and re-think my plans. I had a coil installed in my Koker but have yet to hook it up. My current electric water heater is almost 18 years old and I am going to be replacing it soon. I've already secured an estimate to replace the water heater and plumb the coil, tempering valve,etc. But, I never considered a tempering tank. Before I commit to tying in the coil directly to my water heater, are there advantages to using a tempering tank. I know that if the pressure relief valve blows on my planned setup, water will collect in a catch pan and then drain into my sump crock. I like the idea of being able to route this blowoff for a useful purpose.....or even using some of the heated water for another heating zone?