The purer mountain waters are often acidic, and therefore more corrosive than the hard waters, the dissolved substances of which deposit onto the tubes and plates, leading to them overheating and burning, and which have to be removed, often by mechanical means, at wash out. To avoid these problems water needs to be treated, exactly how should be researched by a water treatment chemist, preferably not from a water treatment firm who will be wanting to sell their products. Whilst tubes and flues can be recycled, it is better that they are worn out before they are removed when this becomes necessary. Boilers left out of doors with water in them between use, are corroding away, and modern day usage with occasional steaming is the worst possible treatment, as continual heating up and cooling down stresses parts tending to cause fractures. Most of the boilers in use today are old, the material far beyond the age of anything that would have been in commercial service.
Boilers wear from erosion from the ash etc, as well as burning from the flames of the fire.
Wet ashes in a smokebox, and water left in the bottom of a barrel or firebox can cause bad corrosion and thinning of plates. Modern welding methods of both steel and copper enable new sections of plate to be welded in, or local areas just to be built up. In the end, the economics of major and expensive patching up of old boilers must be considered against that of building a completely new boiler, many small boilers are now being built new. Allan Garraway MBE is a Vice President of the Heritage Railway Association and HRA Adviser on Railway Operating.