Energy Write is a Resource for Residential Do-It-Your-Self Energy Reduction.
Energy Reduction How to Article ...
Energy Saver: Furnace, Boiler & Woodstove Combustion
(continued ...) On boilers, the other side is a water solution or all water. This cleaning could be the easiest or hardest one of all the tasks. Drain the fluid out of the system and inspect it. As you drain it, collect it in 5 gallon buckets. You'll need to know what the total volume is later. Is it a murky black or brown sludge; very bad?! Is it an iridescent color; a glycol solution? Is it mostly clear; all water? Drain all the fluid out of the system. Go to the highest point and open any vents you can find. If there are no vents, at the highest point where there is a radiator, use a wrench and loosen the pipe at a union to let air in and helping all fluid out at the lowest point.
Remember to measure the volume drained. Glycol solutions can be sent out to a recycling center. Check with your local automotive parts store. Be sure to check the percent glycol with a hydrometer or a test-strip kit. We'll refill the system with new liquid later.
Next, use a mild non-foaming cleaning solution like tri-sodium-phosphate (TSP). You can obtain this at your home center. Follow the label directions to create a medium strength cleaner based on the volume of water you recorded draining out. Refill the system with softened water and the TSP according to label directions *1. Since this is a hydronic (water based) system, there should be a small circulating pump. Use it to circulate the cleaning solution for about 4 to 8 hours. Drain the solution and dispose of properly. Refill the system with plain water; circulate for a few minutes and then drain. ...