[Evans, Marv]

Yes, the valves isolate the heater from the rest of the system. After closing them, you hook lines up to circulate the solution through the heat exchanger, drawing from a 5 gallon bucket of solution and the outflow goes into another 5 gallon bucket (at least that's how I did it). I bought a small submersible pump at Harbor Freight to circulate the solution. After circulating the cleaning solution I circulated plain water. It's an operation but not too involved or time consuming.