Water pipes will become clogged by the accumulation of minerals found in most water. Given sufficient time, this mineral deposit will reduce the flow of water to such a degree as to impair the efficiency of the entire plumbing system.
Galvanized steel pipe is especially vulnerable to this condition because the rough interior of the pipe provides a surface to which the minerals cling. A galvanized pipe that is lined with minerals must be replaced, for there is no effective way to remove the deposit.
Brass pipe is less affected by these minerals, due to its smooth interior. When brass pipe does become lined, the sections of pipe can be taken apart and the minerals reamed out, if the lining is not too thick.
To do this, remove the coil or water back from the fire box of the furnace or stove. This will require a stilson wrench. Some of the mineral deposit can be removed by tapping along the surface of the heating element with a hammer and flushing with water. After this has been done, pour a solution of 1 part muriatic acid to 8 parts water into the water back or through the coil, and use a funnel to avoid spilling the liquid.
Plug the bottom of the coil before pouring in this solution. Take care not to splash the hands, face, or clothes with it. Muriatic acid is strong as well as poisonous. If possible, heat the element with the acid solution inside, as this will quicken the action of the acid on the mineral deposits. If this cannot be done, let the solution remain in the coil or water back for an hour or more, then pour it out. Several treatments may be necessary if the deposit is very heavy.
After removing as much of the deposit as is possible, flush the inside of the heating element with fresh water several times, to remove all traces of the acid. Brass pipe can be cleaned in a similar manner, or the deposits can be reamed out. Galvanized pipe, due to its rough interior, does not clean readily and can be replaced at moderate cost.