Captive air tanks did away with the problem of water logging and also gave the customer far less rusty water than the old-style pressure tanks because the water in the tank and the air were completely separated. This, however, created a whole new situation regarding iron filtration.
In years gone by, my father and I sold a number of cartridge-type filters to customers who had rusty water. After several years, we began to investigate other types of filters that would work on ferric or visible iron.