_a._ Five brass drain cocks, each with a lever handle and of 1/2-inch
bore, are to be provided, and located one on each end of each water
cylinder, and one above the upper valve deck.
Care should be taken to select a pattern of cock whose passageway
is the practical equivalent of a 1/2-inch hole. Some patterns of
1/2-inch commercial cocks although threaded for 1/2-inch pipe thread
have but a 1/4-inch hole through them. Such are not acceptable.
[Footnote D: Such detachable rubber check valves are now made up in
regular form by the George F. Blake Mfg. Co., East Cambridge, Mass.]