Gents, I have Lancaster media filters after my chlorine retention tank, and the first is the larger sand filter, for turbidity and pieces of sediment, and the second is the carbon backflush. After a few months I caught a whiff of a mustyish sulphur in the cold line on the washing machine and similar in the fridge. So I shocked the pipes with chlorine and it went away but came back. Upon inspection my backflush (regeneration as the tank top says) was set at 9 days. I moved this to 5 days and the smell went away. My friend says his is set at 7 days on his similar setup. I think my filter media was loading up. I use about 1,000 gallons a week on a 320 foot deep well that pumps 7gpm so I don't worry too much about using lots of water for something like this. It goes to a daylight drain incidentally. I am told I am using 90 or so gals each backflush but that is the plumbing supply house rep and I can't tell if he really knows a lot. Does anyone want to offer me input as to the frequency they see as needed? Iron bacteria is the smell culprit incidentally. The chlorine seems to work nice, and I have considered going to Hyd. perox. But I hate to tamper with success. Am I backflushing too much, too little, is there a guidepost or set of rules the experts use, or is it kind of different for everyone depending on the pie water issues? The refrigerator ice is the place where I'm most interested in making sure the water is sweet. I have a second Carbon filter going to that in the line to kitchen, a ten inch five micron cartridge. That unit makes it easy to shock just that line and of course I got rid of the fridge water filter and installed the bypass plug. No one wants to be swapping a forty dollar filter every month.