On the badly clogged ones I circulate a weak solution of Muriatic acid (technical-grade hydrochloric acid used for masonry cleanup) followed by a flush with clear water and baking soda to neutralize the acid. About 3-4 ounces of acid to a full fill of water, run it for 15-20 minutes with the thermostat removed, drain and refill with water and 1/2 box of soda- - - -run for 10 minutes and flush with clear water. After the acid/soda treatment, then do the back flush to dislodge the remaining deposits. Then use a 50/50 antifreeze/water mix for -37 degree F. freeze protection.
Jerry
