This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The same care is required as with the stationary fountains. The exterior of iron and steel fountains should be well painted as a precaution against rust.
Portable fountains are intended to resist a high pressure of carbonic acid gas, and should, therefore, be tested at least once every season with hydraulic pressure to double the usual pressure (400 lbs.).
To ascertain if a fountain needs re-lining, empty it of carbonic acid gas by tipping it upside down, then wash out thoroughly, lower a lighted candle into the fountain by a wire, and it can be readily seen whether the lining is worn off or not. A fountain well lined and properly taken care of will last for soda water about five years. It is important that this work should never be entrusted to other hands than those of a regular manufacturer of soda-water apparatus. Coppersmiths used to other kinds of work cannot appreciate nor understand the great strength required in a soda-water fountain, which is at times subjected to a higher pressure than is required even in a steam-engine boiler.
As a fountain has to be taken apart for repairs and re-lining, it would be extremely hazardous to rely upon its being safely put together by a cop-persmith who is not also a regular manufacturer of soda-water apparatus.