Mechanical Contracting & Plumbing January-December 1908 . ration cocks are not as extensivelyused as are threaded corporation cocksfor the good and suilicient reason that they cannot be depended on to remaintight after they have been installed. Asudden jar of the service pipe when thetrench is being filled, a subsequent up-heaval of the service pipe by frost, or asettlement of the street mains, is liableto loosen the corporation cock, thus al-lowing it to leak. If the ground wherethe service is installed is of a loose, por-ous texture, the water will seep awaywithout showing at the surface, an
Mechanical Contracting & Plumbing January-December 1908 . ration cocks are not as extensivelyused as are threaded corporation cocksfor the good and suilicient reason that they cannot be depended on to remaintight after they have been installed. Asudden jar of the service pipe when thetrench is being filled, a subsequent up-heaval of the service pipe by frost, or asettlement of the street mains, is liableto loosen the corporation cock, thus al-lowing it to leak. If the ground wherethe service is installed is of a loose, por-ous texture, the water will seep awaywithout showing at the surface, and ifmany corporation cocks are leaking inthat manner, a large quantity of waterwill be lost daily without any surfaceindications to show where the loss oc-curs. Large Sizes in Special Cases. The size of corporation cocks used isa consideration about which water com-panies are very particular. Most com-panies are very particular. Most com-panies have a certain size corporationcock, which they use generally, and alarger size which they will insert in spe-. Service Connection to Water Main. cial cases. If the large corporation isnot of sufficient size to supply the re-quired amount of water, they will con-nect the service to several taps, or willcut the ^reet main and insert a specialbranch fitting for the service pipe. Thelargest corporation commonly permittedby water companies is % inch. As arule, they object to a larger size, par-ticularly on small mains, because onaccount of the curvature of the pipe, asufficient number of full deep threadscannot be tapped to insure a tight is more particularly true of small?pipes which have a small arc, than inlarge water mains of 24 to 36-inch diam-eters where much larger taps couldsafely be used. Corporation cocks ofy^-inch, %-inch and %-inch diametersare the sizes commonly used in practice,the %-inch being the largest generallypermitted. Corporation cocks are used for tworeasons. In the first place, the use of acorporation cock
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