A fair amount of our work involves flow testing fire hydrant systems to determine or verify the amount of available water for fire protection. It is not uncommon for us to encounter lower available flows than expected due to tuburculation in the water main. Of course, this is exactly why fire hydrant flow testing is so important...especially in older systems that used unlined ductile iron pipe. Even the 10-inch water main shown in this photo has significant tuburculation.