Yesterday, I had to vacuum the sediment out of both water heater tanks, flush with fresh water for about 15 mins, then vacuum. I did this 4 times for each heater and I think they are pretty clean for 28 years old. The new elements are installed, powered up, and started to heat the water. I only gave them about 15 minutes checking voltages on the heaters, thermostat and cutout, the water didn't have enough time to get hot but it was warmer. I will leave the system pressurized and heaters off overnight to see if there are any leaks before I button it up. I will be glad to put the water system behind me so I can move to the Webasto.