Circulation cut my heat up time by a lot. The sump pump is way too powerful for this use but it showed that the unit will heat the water to 148 in less than 4 hours. It was already to temp when i got back to the house from a run to the store so i'm not sure exactly how long it took but it was quite a bit less than the original test. I'm going to buy a small pond pump and rig it to the extension cord so the pump will always run even if the thermostat shuts off. If the pump will sustain operation in 150 degree water I think the build will be a raging success. Testing now to see if the water temp can hold with the lid off. Cheers.