I recently moved into an old farm house which has a very bad sulfur well water problem. There was a culligam chlorine system already in place. Unfortunately with such high sulfur 60ppm the chlorine system was unable to properly treat the water. System injected straight chlorine into a 250 gallon holding tank. So we would go from extremely high chlorine to strong sulfur smell. Could never get system regulated. Culligan recently installed a new hydrogen peroxide system with secondary chlorine treatment. System worked great for a week or so with no smell at all. After the first week the water began to smell like sulfur again. Slowly at first and got worse each day. If we run the water hot or cold for a few seconds the smell would go away. Over time the time needed to run the water before the smell went away increased. Can anyone provide the reason for the increase smell over time? Culligan says that this is common. Seems that once the lines are flushed the water in good but why is this happening?