Zinc coatings on the surface of galvanized iron pipe are attacked and dissolved by some waters almost as energetically as is lead pipe. Zinc is also dissolved to a considerable extent from brass pipes. At Cwmfelin,* in Wales, galvanized iron pipe that conducts water from a spring to the town, a distance of one-half mile, was found to change the character of the water as shown by the following analysis:

Table XVII - Lead In Samples Of Surface Waters, Arranged According To Average Amount Of Lead Found When Water Is In Ordinary Use

(Report Massachusetts State Board of Health, 1900, page 491.)

The effect on ground and surface waters that are conducted through galvanized iron and brass service pipes can be judged from the results in Tables XIX, XX, XXI and XXII.

To briefly sum up, it may be stated that it is always better to determine experimentally the action of water upon pipes than to try and predict it from a knowledge of the character of the water. It is better still to only use pipes that are not affected to any appreciable extent by the solvent action of any water. If, however, pipes must be used that are so affected, then those should be selected, the dissolved metals of which are the least injurious to the human system.

The necessity of using pipes that are not injurious is manifest, when it is considered that a water which is perfectly wholesome and non-solvent may be changed at any time for a different supply that might energetically

Table XIX - Zinc In Samples Of Ground Water. (Parts Per 100,000 )

(Report Massachusetts State Board of Health, 1900, page 495.) attack the pipes, or, the character of the water itself might change sufficiently to dissolve the metal.

Copper is also dissolved from brass pipes, as may be seen from the following tables of analysis of ground and surface waters drawn from brass service pipes.

Table XX - Zinc In Samples Of Surface Water. (Parts Per 100,000.)

(Report Massachusetts State Board of Health, 1900, page 495)

The effect of some water upon different metals of which water pipes are made or coated, and the resultant effect upon the health of those drinking the waters are shown in Table XXIII.

Table XXI - Copper In Samples Of Ground Water (Parts Per 100,000.)

Table XXII - Copper In Samples Of Surface Water (Parts Per 100,000.)

Table XXIII - Effect Of Metals On Health

The action of water upon galvanized iron pipes is almost as energetic as upon lead pipes, and under suitable conditions will dissolve equal amounts of metal from each. However, the effect of the zinc upon the health is not dangerous but only injurious, because zinc is not a cumulative poison, and so long as the initial dose is not sufficient to cause illness or death, the effect is soon thrown off without apparent injury. Lead, on the contrary, even when taken in small doses, remains in the system until sufficient poison accumulates to cause serious illness or death, or if the initial dose is of sufficient strength the effect may be immediately fatal.

* Dissolved iron or rust in small quantities is not injurious to health, but 1/4 grain of iron per gallon of water imparts an objectionable taste to the water besides making it unfit for washing and for most manufacturing purposes.

Lead pipes are more extensively used than any other kind of pipes for water supply in buildings. Sheet lead also is extensively used for lining water tanks. Within the past few years, however, a rational decrease in the use of lead supply pipes and lead lined tanks is noticeable. Galvanized iron pipes, which are cheaper and better in every way, are fast supplanting lead pipes, and when perfect security from metal poisoning is desired, Benedict nickel seamless tubing, tin-lined lead, or tin-lined iron pipes may be used. From a hygienic standpoint, Benedict nickel and tin-lined pipes are about equal, but when superior finish is desired the Benedict nickel tubing will be found the more satisfactory. In appearance it is equal to nickel-plated brass pipe, and in all other respects superior to it.