Well, I finally did it, after lots of research and contemplation, bought a Central 5036 on Friday, been fired only 2 weeks, good condition, saved mucho $$, dealer will honor full warranty, but will not be getting it on line until this coming fall. He showed me a water sample from it, and it looked a little yellow (sulfur?), and recommended I fill it and hang a circ. on it and keep the water flowing thru it until I get my piping and install done. Has anybody tried TSP, or any other boiler water cleaner, other than the PH and corrosion inhibitor that CB sells?