It has been too warm in MO lately to run my rocket stove heater, but I still want to cash in on heating my water with it. To do this, I turned the central heat blower off and left the pump running. By using a small fire fueled with brush from trees I cut down, I can keep the water nice and hot without boiling. Here's a quick video I did on it:
It also enables me to use nearly all of a tree, the large wood in the cold weather to heat the house and water. The brush is used in the warm weather to heat just the water.