The great industry don't produced and used fittings that would be a deceleration in an atmospheric aqueduct. Local artisans used all the fittings, building bends, flanges, weldolets in loco, for small plant. Nerva emperor delegated Frontinus, a very important official public man, to recover the defrauded water that was an half of the total. The roman valves are bronze according to the normalization of dimension, material, drawing. The functional equipment, is beautiful.
Bronze is rich of lead, antifriction, without gasket, anticorrosion, ductile, easy to turn.
The bronze is now a ASTM B. 67. For pressure pipelines the industry produced a large quantity of bronze valves, normalized by engineering. Lyon aqueduct was equipped with 15.000 tons of pipes and valves. Ostia Antica was equipped with great underground pipelines to serve water to the town and to the ships. Local artisans built little valves around the world with some difference in drowning as we have seen in Rabat, in Djemila, in Instanbul, or in Avenches, in Augst, toy butterfly tap, or in Naples the valves with the circular stem.